Pre- and early Roman times

The earliest settlements on Trier city territory have been proven near the later Roman potteries on the banks of the Pacelli River. These are finds of the Linear Pottery Culture.^[2] Already in the pre-Roman Iron Age, the Trier valley may have been largely cleared and settled. Before the first verifiable Roman bridge over the Moselle was built in 17 B.C., there was probably already a ford at the site.^[3] In the late Latène period, settlement seems to have been scattered along the right bank of the Moselle. A concentration of settlement features could be found during an area excavation between the Moselle, St. Irminen, Ostallee and Gilbertstraße.^[4]

The important centers of this time are not assumed to be in such valley settlements. The Treverian tribe, which gave its name to Trier, is tangible in the region mainly through important hilltop settlements (oppida), among them the oppidum on the Titelberg in Luxembourg, the Castellberg near Wallendorf, the Hillfort of Otzenhausen or the oppidum on the Martberg.^[5] The Treverian tribe was the first to settle in the region.

However, the small settlement was reason enough for a Roman military station to be established above the Trier valley width on the Petrisberg a few years after the Roman conquest of Gaul under Gaius Iulius Caesar. Few finds, among them Arretinian terra sigillata as well as a dendrochronologically dated wooden fragment, point to the time around 30 B.C.^[6] A connection with Agrippa's road building measures is suspected, which are mostly attributed to his first governorship in Gaul in the years 39/38 B.C.^[7]

Foundation

The city was probably founded in 18/17 BC by Emperor Augustus, which is primarily indicated by the name, but which is documented only in later times. The honor of being called by its name was otherwise only given to Augusta Vindelicum (Augsburg) and Augusta Raurica (Augst) in northern Switzerland in today's German-speaking world. The exact date cannot be determined from the sources and can only be approximated. The following are considered to be fixed historical points:

• The reorganization of the Gallic provinces under Augustus, which began in 27 BC with a census and concluded in 12 BC with the foundation of the altar of Roma and Augustus (ara Romae et Augusti) at Lugdunum (Lyon). Within this period, the foundation of a central place of the Treverians could also be assumed.^[8]
• The second governorship of Agrippa in Gaul in 19 BC^[9]
• The stay of Augustus in Gaul 16–13 BC.^[10]

This period can be significantly limited by archaeological finds. In the first place, the foundation piles of the first Roman wooden bridge over the Moselle are to be mentioned here. They prove that in the context of the road construction measures of this time the bridge was built in the years 18/17 B.C.^[11] Fragments of a monumental inscription for the Augustus grandsons Lucius and Gaius Caesar, who died in the years 2 and 4 A.D.^[12], show that at the latest at the end of the reign of Augustus certain urban structures were present, since such an inscription is only conceivable at public places with the function of a central place. An evaluation of the early Roman finds from the city area has shown that a large-scale settlement cannot be expected before the late Augustan period (Haltern horizon). This coincides with the abandonment of the settlement on the Titelberg, so that here possibly a transfer of the administrative tribal center of the Treverians is present. Similar building programs can be traced throughout Gallia Belgica and neighboring regions on the Rhine and Danube in this period.^[13]

Early and high imperial period

Augustus' measures in the Gallic provinces included the tripartition of the former Gallia comata into the new provinces Gallia Aquitania, Gallia Lugdunensis and Gallia Belgica, with Trier becoming part of the latter with its capital at Durocortorum Remorum (Reims). Trier was the seat of the financial procurator responsible for Belgica and later for both Germanic provinces (procurator provinciae Belgicae et utriusque Germaniae).^[14]

While only uncertain information can be given about the settlement at the time of the foundation,^[15] the development into a planned colony city is well recognizable in the 1st century. The street network deviates in the northern and southern outskirts more strongly from the regular layout of the insulae, so that for the core area a square foundation city with the width of three insulae results. Near the river, a considerable backfilling was carried out towards the end of the 1st century in order to gain flood-free usable areas. Several pillars of the Moselle bridges were filled up in the process. Also at the western bridgehead of the pile-grate bridge was a triumph arch-like gateway.^[9]

Neumagen wine ship in the Rhineland Regional Museum Trier

Trier saying cup, place of discovery Krefeld-Gellep (Gelduba)

The earliest mention of the stone bridge over the Moselle can be found in Tacitus' account of the Batavian Revolt of 69 A.D.^[16] Tacitus also mentions that Trier was a colony city (colonia Trevirorum).^[17] Presumably, similar to Cologne, the city had received this privileged status under Emperor Claudius.^[18] As terminus post quem can be seen a milestone from Buzenol from the year 43/44 A.D., which refers to Trier only as Aug(usta), not as colonia.^[19] However, unlike Cologne, the founding of the colony here was not connected with the settlement of legion veterans, i.e. Roman citizens. Therefore, there are basically two different views on the nature of the Trier colony status. One interpretation assumes a pure titular colony; unlike in the case of a regular colonia, the title colonia was not connected with a conferral of the civitas Romana to all free inhabitants. Opponents of this thesis have pointed out that there is no evidence for such honorary bestowals, and instead assume a bestowal of the latin rights.^[20] It is also unclear whether Tacitus used the designation in a legally precise manner or only as a general characterization.

The legal status of the city dwellers and the tribal community of the Treverians in the imperial period is thus not entirely certain. It is noticeable that, on the one hand, the designation as Treverians (Treveri or cives Treveri) continues to be used in inscriptions, which does not allow any conclusion on the civil right.^[21] On the other hand, mentions of the city (colonia) and the tribal community (civitas) suggest that both could have existed in parallel.^[22] Regardless of the legal status of the Treverians and their civitas, the city of Trier as their capital was an integral part of the Romanization. Already in the 40s of the first century, the geographer Pomponius Mela mentions Trier as a flourishing, rich city (urbs opulentissima).^[23] The value of this news is, however, controversial, since Mela still follows the tripartite division of Gaul from Caesar's Gallic War and does not mention important cities such as Lugdunum or Cologne.^[24]

However, the archaeological evidence testifies that in the 1st century the place took a rapid upswing. Numerous buildings were erected, such as the forum baths at the cattle market around 80 or the amphitheater around 100. In the middle of the second century the thermal baths at the cattle market had already become too small, so that one built over the surface of several Insulae the Barbara Baths. In their time they were considered one of the largest thermal baths in the Roman Empire. Under Marcus Aurelius and Commodus, the city fortifications were built from 170 and with them the north gate, the Porta Nigra, which underlines the importance of the city in the 2nd and 3rd centuries.^[25] Possibly, the construction measures are connected with the elevation of the city to the provincial capital of Gallia Belgica. The period when Trier replaced Reims in this function cannot be stated more precisely than before the middle of the 3rd century.^[26]

The basis of the city's rise was, in addition to its convenient location on the Moselle and the roads leading into the interior of Gaul, trade and commerce. Trier's terra sigillata manufactories, along with the potteries of Rheinzabern (Tabernae), attained a dominant position in the market in the late 2nd and 3rd centuries.^[27] The associated workshops were located mainly southeast of the city on the banks of the Pacelli. Also very popular in the northwestern provinces of the Roman Empire were the so-called Trier Spruchbecher, engobed cups inscribed with toasts.^[28] Occasional references to crafts and trades are preserved on stone monuments with which urban elites represented themselves. An indication of the trade is given by the Igel column, grave monument of the cloth merchant family Secundinius, on whose reliefs various activities of cloth production and trade are depicted. Already in Roman times, the cultivation and trade of wine may have played a not insignificant role,^[29] to which, among other things, the Neumagen wine ship refers.

In the civil war of the years 193 to 197 (Year of the Five Emperors) troops of Clodius Albinus besieged Trier, which was on the side of his rival Septimius Severus. The city was able to withstand the assault and was finally relieved by an army brought from Mainz, which the city later thanked in a preserved inscription.^[30] Both the discovery of a large Trier Gold Hoard from 196/197 and the fact that work on the Porta Nigra was apparently never fully completed are associated with this siege. It can be assumed, however, that the ultimately victorious Severus rewarded the city for its loyalty afterwards, as was customary in such cases. Due to its location in the hinterland, Trier was spared for a long time from the Germanic invasions during the so-called imperial crisis of the 3rd century, which led to the abandonment of the Upper Germanic-Raetian Limes (Limesfall). The residence of the Gallic Special Kingdom, which was created in the turmoil of the crisis, initially became Cologne. In the last years of the special empire, however, the residence was moved under Tetricus between 271 and 274 to Trier, which was safer because of its location.^[31] Since the city seems to have proven itself as an imperial residence and administrative center in the process, this measure pointed to the future. Soon after the death of Emperor Aurelian in 275, however, the city was initially sacked and partially destroyed by marauding Franks and Alamanni.^[32]

Late antiquity

Between 293 and 401, Trier was then one of the most important places in the west of the Roman Empire. As a result of the Diocletian reforms, the city became the seat of the praetorian prefect Galliarum and thus the administrative center of the diocesis Galliarum, which encompassed what is now Western Europe and parts of North Africa. The province of Belgica was divided and Trier became the capital of the Belgica prima thus created. During the Tetrarchy, first the Caesar Constantius I chose Trier as his residence in 293. Later, his son Constantine I, who stayed in the city for several years between 306 and 324, expanded it in a representative way. In order to consolidate his claim to power – which contradicted the actual rule of succession to the throne – in propaganda terms, Constantine had a monumental palace complex built (even by late antique standards) on the model of the Palatine in Rome.^[33] One of the ways in which he legitimized his rule was by deifying his father, who was buried in a mausoleum near the present-day church of St. Maximin. The construction of the Imperial Baths and the Palastaula, the largest known example of this type of building, also began during this period. On the banks of the Moselle near St. Irminen, a large double storage facility (horreum) from the 4th century was also discovered.

Attracted by the imperial court and the comitatenses stationed in the surrounding area, many people settled in the city, and the population probably multiplied. Exact figures cannot be determined due to a lack of knowledge about the built-up area within the city walls. For the middle imperial period it is assumed that there were about 20,000 inhabitants, of whom about 18,000 would have found room in the Trier amphitheater. The Circus, built in the 4th century, on the other hand, held at least 50,000, perhaps even 100,000 visitors, but in neither case can it be said whether consideration was given to the population of the surrounding countryside when these buildings were planned.^[34] More than 100,000 people will hardly have lived in Trier even in the 4th century; other considerations even assume that even in late antiquity a population of more than 30,000 could hardly have been supported in this area. After the departure of the imperial court and the praetorian prefecture in the early 5th century, the city's population may have declined quite rapidly to perhaps 10,000 at last.^[35]

Follis of Constantine, Trier mint ^[36]

Constantine's son Constantine II resided here from 328 until his death in 340, the usurper Decentius from 351 to 353. Treveris was again the residence of Roman emperors (Valentinian I, Gratian, Magnus Maximus) from 367 to 388; the young Valentinian II resided here again around 390. This period of prosperity was also reflected in the literature of the time. The imperial educators Lactantius (around 317) and Ausonius (367–388) worked in Trier; the latter set a literary monument to the landscape in his Mosella. Under Ausonius, the Trier College also achieved its greatest importance. It was one of the most important schools in the Western Empire, surpassed only by the school in Burdigala (Bordeaux). Although there are some written sources about it,^[37] an exact picture of the school cannot be gained.^[38] The most important son of the late antique city was Ambrosius of Milan.

The presence of administrative and military personnel, the court and the mint increased Trier's importance in the 4th century. Several palatial villa complexes attributed to the imperial house or high officials, such as the Palatiolum in Trier-Pfalzel, were built in the city's environs.^[39] The disadvantage of this development was a considerable forced economy to supply the city and the court; the withdrawal of the institutions around 400 left a gap that could not be closed. The proximity to the imperial residence meant a certain security in this period; in other parts of the Roman Empire, the villae rusticae, like the entire rural settlement, were severely threatened, so that only the fortified towns offered protection to the provincial Roman population.

Probably around 402, a few years after the transfer of the court to Mediolanum and the death of Theodosius I (395), the Gallic praetorian prefecture was also transferred from Trier to Arles (418 at the latest). With the departure of these important economic factors began the final decline of the once important Roman city. All that remained was the episcopal administration, with which Christianity became the bearer of the continuity of Roman culture, supported by the Gallo-Roman upper class, which continued to be influential. After repeated destruction and plundering, the city finally fell to the Franks around 480. Roman rule in northern Gaul existed only nominally at this time: while the Romanized Frank Arbogast had ruled in the area of Trier until then, the Gallo-Roman special empire established by Aegidius in northern Gaul after 461 continued under his son Syagrius until 486/487.^[40]

Imperial mint

Solidus of Valentinian II, Trier Mint

According to the finding of several inscriptions^[42] it could be assumed that already the Gallic usurpers had coins struck in Trier. However, the attribution of Gallic coinage to Trier is problematic; the minting of imperial coins at the Trier mint is only certain from 293/294, under Caesar Constantius I. The Trier mint was one of the most important mints of the Late Antique Empire. During almost 150 years, 39 emperors, usurpers, empresses and emperor's sons were minted on coins in Trier, including all emperors ruling in the western part except Jovian. Known are more than 520 gold, 310 silver and 1250 bronze coins with different obverse and reverse. Trier mintages were mostly marked by the letter group TR.^[43]

The latest mintings of the Trier imperial mint are from the usurper Eugenius (392–394). It is disputed whether minting still took place under Honorius (395–423), since calibration weights with the name of the emperor have been found, but so far no corresponding coins are known.^[44] The coins of the Trier imperial mint were minted by the usurper Eugenius (392–394).

Franconian time

The frequent warlike events and changing power relations associated with the collapse of Roman rule permanently changed the settlement pattern in the 5th century. Backfills of the underground service facilities in the Imperial and Barbara Baths prove that operations were abandoned in the first half of the century. The Ruwer water conduit could also no longer be maintained and was abandoned. At first, only small parts of the previous urban residential quarters were used. Large parts of the moat in front of the northeastern city wall were filled in because it was no longer defensible due to its size. The large buildings of the former imperial residence probably served as a refuge for the population.

From the middle of the 5th century on, the finds are extremely sparse and are mostly limited to church buildings such as the double church complex Dom/Liebfrauen and the church of St. Maximin, where a gapless sequence from the late antique coemeterial building to the early medieval church can be proven. Furthermore, the cemeteries south and north of the city were used, whereby the name material of the early Christian inscriptions shows a high Romanesque population.

Finds from the older Merovingian period are rare in the urban area. In the Altbachtal a small hamlet can be proved since the 7th century, which is partly built on the ancient ruins. While the finds of the 6th century were limited to isolated finds and the area of the veneration of saints and relics around the suburban churches, an increase in population can be expected since the younger Merovingian period. In the city center, the Roman street network remained partially in place until the market was established at the Domburg in the Middle Ages.^[45]

Forum

The city's forum was located at the intersection of decumanus maximus and cardo maximus. Only a few statements can be made about the early period of the complex. In Vespasian times it was greatly expanded so that it occupied six quarter areas on either side of the W-E axis of the city, measuring 140 × 278 meters. During the expansion, some private residential quarters were leveled as well as the neighboring forum baths at the cattle market were added to the complex. At the western end of the forum was a basilica (100 × 25 m), which occupied the entire width of the square. East of it, on both sides of a long rectangular square along the main street, were porticoes with underground cryptoporticos and stores.^[50]

Victorinus mosaic with inscription

On both insulae west of the forum, early residential development of the 1st century was first identified. It was replaced in the northern insulae (under the present city theater) in the 3rd century by a distinguished town house. It had a large inner courtyard with portico (peristyle house) and a rich decoration with marble paneling, wall paintings and mosaics. The inscription on one of these mosaics identifies it as the residence of the Praetorian tribune Victorinus, later emperor of the Gallic Roman Empire.^[51] Mighty wall courses on the two southern insulae can be added to symmetrically adjoining buildings in this phase, so that public buildings are presumed to have been built here.^[52]

City fortification

Already the city of the 1st century A.D. had archways at the borders of the civil buildings, which, however, did not have a fortificatory character, but were designed as triumphal or honorary arches. Foundations of such buildings could be proved archaeologically at the city-side bridgehead of the Moselle bridge, between Simeon- and Moselle-street as well as a blocked rest in an arch of the imperial thermae. They probably formed the conclusion of the founding city of the 1st century even before the construction of the Circus and the amphitheater.^[47]

The 6418 m long Roman city wall then enclosed an area of 285 ha. In the past, it was often assumed that it was not built until the 3rd century, when civil wars and marauding Germanic tribes threatened the cities of Gaul. Today, however, there is a consensus that the city wall was already built in the last quarter of the 2nd century. This dating results, among other things, from the fact that it cuts through parts of the burial ground there in the north at the Porta Nigra.^[53] The latest burials within the walls date to the third quarter of the 2nd century. (The Romans generally buried their dead outside the city walls, so the graves must be older than the wall). Small finds in the wall area point to the late 2nd century. To the south, the wall cuts through the pottery district, which, however, continued to produce on both sides of the wall in the 3rd century. Markings on the stones of the Porta Nigra also refer to Emperor Marcus Aurelius (161–180) and his son Commodus (180–192). The complex appears to have been ready for defense when Clodius Albinus' troops attacked the city in 195 to no avail.

The wall was built as a typical Roman cast masonry. The core consisted of slate, small stones and abundant mortar, while sandstone or limestone ashlars were faced on the outside. The height of the walkway can be reconstructed to 6.2 m based on the preserved wall exits at the Porta Nigra. The width was up to 4 meters in the foundation area, reduced to up to 3 meters at the end.^[54] Round towers were regularly inserted, mostly at the ends of the street alignments. The total of 48 or 50 towers of the Trier city wall still protruded evenly from the wall on both sides. Later Roman fortifications, on the other hand, usually had towers projecting far outward, which allowed the lateral areas of the wall to be better protected and attackers to be caught in the crossfire. The shape of the towers also indicates that they were built in the late 2nd century.

Modern research mostly assumes that Trier's city wall – similar to those of many other Roman cities in the predominantly peaceful 1st and 2nd centuries – was not built to respond to a concrete threat; it was less a military installation than a prestige project intended to underline the importance of the site.

Of the wall, only in the north and along the Moselle are smaller sections preserved, which were integrated into the later medieval city wall (Schießgraben, at the vocational school; cellar of the house at Schützenstraße 20, visible from the outside). In the southern sections it was excavated down to the foundations. On Langstraße, a part is accessible along the length of 70 m.^[55]

The city wall had a total of five gate buildings, some of which, like the Porta Nigra, were very elaborately designed and at the time of their construction already anticipated the later widespread type of fortified gateaway. The southern gate (Porta Media) opposite the Porta Nigra was already demolished in the Middle Ages, which is why only foundations are known of it. The western gate at the Moselle bridge continued to be used in the Middle Ages and was called Porta Inclyta ("famous gate") at that time. From the east, the city was entered through a gate south of the amphitheater, which was used as a secondary entrance. In the late 4th century another southeast gate was added, which since the Middle Ages was called Porta Alba.

At the time of its construction, the spacious fortification was still designed for growth, as many open spaces in the peripheral areas show. In military terms, however, the wall was of little use. The structure hardly had to prove itself in the first 200 years of its existence – the only known exceptions are the attack of 195 and the Frankish-Alamanni attack around 275, and in the latter the wall could not stop the attackers. Then, in the 5th century, it was hardly possible to effectively defend the city with the complex designed more for representation than for defensive value. Before the attack of the Vandals as a result of the Crossing of the Rhine, the remaining population of the city, which had been cleared of court and administration, could only protect itself by entrenching itself in the amphitheater.^[56]

Porta Nigra

Main article: Porta Nigra

Porta Nigra, city side

The Porta Nigra is the only surviving gate of Trier's Roman city wall and, along with the Imperial Baths, probably the most famous monument. Like the city wall, it originally dates from the last quarter of the 2nd century AD; the start of construction could be dated to the year 170 by dendrochronology in 2018. It owes its preservation to the fact that in the Middle Ages Simeon of Trier settled in the building as a hermit, and the northern gate of the Roman city was subsequently converted into a church. By Napoleon's order it was freed from later additions since 1804.

Porta Alba

The Porta Alba was added in the 4th century as a southeast gate and was located on the road to Strasbourg (Argentoratum). It was narrower than the older city gates and had only a simple gateway. Its name comes from the Middle Ages, when it was variously used as a protective castle.

Amphitheater

Amphitheater

The amphitheater at the foot of the Petrisberg was built around 100 AD, possibly already having a smaller, wooden predecessor. The spectator tiers (cavea) were sunk into the hillside, and the resulting spoil was used to fill in the tiers on the valley side. Of the complex, which could seat up to 18,000 people, essentially the oval arena (70.5 × 49 m) with its boundaries and some underground vaults (vomitoria) have been preserved.

When the city wall was built, the amphitheater was integrated into it and served as the eastern access road. In the Middle Ages, the amphitheater fell into disrepair, was used as a quarry, and the arena was gradually flooded. Since the excavations at the beginning of the 20th century it can be used again for events. In the find material, which is kept in the Rhenish State Museum in Trier, a group of curse tablets, which were deposited here in antiquity, is particularly interesting, in addition to stone monuments.^[57] The rest of the find material dates mainly from the 4th century, which is probably related to the long period of use. Bloody games in the arena are documented as late as the time of Constantine.

Polydus mosaic in RLM Trier

Circus

The Roman Circus of Trier has not been preserved and can only be guessed from the course of some streets below the amphitheater and Petrisberg. Its location is indicated by the clear intersection in the course of Egbert- and Helenenstraße, while the northern rounding may have been located at today's Agritiusstraße. This would result in a complex with a length of about 500 meters.

Chariot racing played an important role in the self-portrayal of the Roman emperors, especially in late antiquity, and enjoyed great popularity. Numerous pictorial representations point to the Trier Circus. First and foremost is the Polydus mosaic, which shows a charioteer with his team.^[58] A similar depiction exists on a contorniate found in Trier,^[59] and there is also a relief with a horse driver in the Neumagen funerary monuments. Since the Treverians are described in the written sources as good horsemen, it is assumed that soon after the amphitheater was built in the 2nd century, a horse racing track was also erected. At the latest, however, when the place became the emperor's residence, there must have been a circus.

Due to its location, the Circus was destroyed faster than other large Roman buildings in the early Middle Ages, the stones were reused and the area was used for agriculture. In the 19th century, the area south of Trier's main train station was developed with a residential area, and the probably very small remains of the site were not investigated.

Thermal baths

View into the reconstructed parts of the thermal complex at the Viehmarkt

Thermal baths at the cattle market

Main article: Forum Baths, Trier

The baths at the Viehmarkt are the oldest public thermal baths of Augusta Treverorum. They occupied a complete insula north of the Roman forum in the central area of the settlement. The baths were built in place of an older residential development around the year 80. Coin and pottery finds make a use with several alterations until the 4th century probable. Whether the site is really a pure thermal complex is disputed. Remarkable is the fact that the necessary heating facilities were added only in a second construction phase, according to other information even in the 4th century.^[60]

The rooms visible today were overformed since 1615 by the construction of a Capuchin monastery. The cattle market was created only after the dissolution of the monastery from 1812. Due to smaller channel excavations and observations in the post-war period, a larger palace-like building had been expected here. During excavation work for the construction of an underground car park and the main building of the municipal savings bank, the thermal baths were discovered from October 1987. Parts of the complex are accessible today together with an exposed road in a glass protective structure designed by architect Oswald Mathias Ungers under the Viehmarkt.

Barbara Baths, state 2007

Temple

Temple at the Herrenbrünnchen

After the discovery of several architectural parts of the 1st century above the temple district in the Altbachtal, an excavation was carried out by the Rheinisches Landesmuseum on the grounds of the Charlottenau estate in 1909/1910. The remains of a monumental podium temple with a columned vestibule (pronaos), flight of steps, and altar podium were uncovered on an area of 65 × 23 m.^[63] The building had walls up to 4.1 m thick. Architectural elements found allow to reconstruct a temple front with six 15 m high columns supporting architrave and pediment. Several elaborately designed capitals in the Trier Cathedral, which were installed to replace granite columns that had been broken after a fire in the 5th century, may have come as spolia from the temple at the Herrenbrünnchen.

Trier gold hoard from the Feldstraße in the Rhineland Regional Museum

Temple of Asclepius

Near the Roman Bridge and north of the Barbara Baths was one of the most monumental temples of the Roman city. Its remains were uncovered in 1977–1979 during the construction of an underground car park. The complex occupied an area of 170 m × 88 m, more than a complete insula width. For its construction, considerable embankments were made along the river for flood protection. Together with the large buildings of the Barbara Baths, the temple probably dominated the cityscape above the Moselle Bridge to a large extent.

A marble sculpture, now lost, and the inscription of a financial procurator^[64] point to the dedication to the god Asclepius. An exceptionally large hoard of coins was discovered at the northern edge of the complex in 1993. It contained 2570 aureus with a total weight of 18.5 kg. The latest coins date from the reign of Septimius Severus, and the hoard of coins is now in the Rheinisches Landesmuseum.^[65] The construction of the temple itself can be placed in the last third of the 1st century A.D. based on the find material.^[66]

Today's spring at Irminenwingert

Roman bridge

View of the Roman bridge from the east

Bridge pile (Trier), second Moselle bridge, 71 AD.

The Roman bridge over the Moselle, which is visible today, had at least two predecessor buildings, which have been proven archaeologically. This can be explained by its location on the Roman trunk roads, but the Roman bridge also had to accommodate inner-city traffic to the Vicus Voclanionum,^[68] which is attested in inscriptions on the western bank, as well as to the Lenus Mars temple there. The dendrochronological evidence of a bridge in 18/17 BC^[69] is thus an important fixed point for the foundation of Augusta Treverorum.^[11]

This first wooden bridge construction apparently suffered damage during the battles mentioned by Tacitus in the Batavian Revolt in 69.^[16] The construction of a pile-grate bridge can be fixed to the year 71 in the reign of Emperor Vespasian. It received mighty, pentagonal stream piers from up to 31 cm thick oak trunks, which were rammed into the river. The bridge piers were made of limestone, and the roadway was supported by a beam truss structure.

The present Roman bridge was built between 144 and 155 under Antoninus Pius. Above the existing bridge, new stream piers were erected, but they were no longer made of wooden piles but of limestone ashlars up to six courses, which is why this bridge is called a stone pier bridge. Since considerable fill was made on the city side bank in the early imperial period, this bridge required only nine piers instead of eleven. Towers and gates at both bridgeheads protected the structure. Probably due to the increased water level caused by the narrowing of the river and problems with flooding, the bridge was initially not given a solid stone arch, but a wooden deck that had to be replaced regularly. This was not added until 1343 under Archbishop Balduin of Luxembourg.^[70] Significant are the numerous river finds from the bridge area, which are exhibited in the Rheinisches Landesmuseum. Among them are tools, coins (as river sacrifices), lead seals, jewelry, small bronzes, and even stone monuments.^[71]

Water supply

The supply of drinking water to the city was particularly favored by its geographical location. In addition to the river water of the Moselle, several streams flowing into the Trier valley from the east could be used. Spring outlets in the city area were captured and connected to the local water pipes. Healing springs such as the so-called Römersprudel southeast of the city were also provided with spring catchments. On the Lower Terrace, additional wells were dug on groundwater-bearing strata in the private sector, while on the Middle Terrace these extended to strata in the slaty subsoil with water flowing down to the valley. A canal line led from a spring at Heiligkreuzberg to a distribution chamber near the temple at Herrenbrünnchen. Two successively constructed distribution basins were uncovered on the site of the Imperial Baths.

For the founding city of the 1st century, these facilities were initially sufficient. To meet the needs of the growing city, the Ruwer Valley water pipeline was built in the early 2nd century. It carried water, diverted from the Ruwer River at Waldrach, over a distance of 12.798 km to the city, which it reached at the amphitheater. It is a masonry walkable canal, which was led in sections (valley cut of Kürenz, proven at the Imperial Baths) via aqueduct constructions.

Further distribution in the city was by masonry canals lined with waterproof opus signinum aggregate; in the outer districts there is occasional evidence of pipes in wooden logs with iron dike rings. Of more upscale design are water pipes made of lead; like the wooden logs, they were usually about 10 Roman feet (3 m) long.^[72]

Late antique buildings

Already in the 2nd century, a representation and administration area had been created in the northeast of the city by merging four insulae, the core of which was a central hall, which is addressed as the Palace of the Legates. The remodeling from the beginning of the 4th century in the context of the establishment of the imperial residence is also concentrated in this area, although smaller construction measures in the forum and the streets of the city are attested. By laying down a residential quarter, space was made for the monumental building of the Imperial Baths. The Palastaula (Constantine Basilica) was built on the former legate's palace, which, with surrounding forecourts and outbuildings, formed the core of the residence.^[73]

At the same time, the backfilling with rubble of an old arm of the Moselle, which had formed a lake until this time, indicates large-scale demolition work within the city.^[74] Also near the harbor on the Moselle, a large double storage facility (horreum, ca. 70 m × 20 m) was built around 300 on the site of today's Vereinigte Hospitien, which served to supply the city and the imperial court. Several walls of it, divided by blind arcades, have been preserved.^[75]

However, construction activity already came to a standstill in Constantinian times. It was probably not completed until the reign of Gratian around 379. Basilica, Imperial Baths and the Circus formed a unit as a palace district. The juxtaposition of the Circus and the residential area was deliberately created as a parallel to the urban Roman topography (Circus Maximus and Palatine). It is repeated at the Circus Neronis (in Caesar's gardens), the Villa of Maxentius on the Via Appia, and the residence of Galerius at Thessaloniki.^[76]

Imperial Baths

Main article: Trier Imperial Baths

East side of the Imperial Baths

Today, the Imperial Baths are one of the most famous Roman buildings in Trier. The time of their construction is not completely clear; they were probably built after 294, when Trier was developed into a residence. Whether they were commissioned by Constantius I or his son Constantine is unknown. The oldest settlement of the area consisted of simple wooden buildings with cellars and storage pits; it can probably be dated before the middle of the 1st century. After that, two larger stone buildings were built, which were later combined into a magnificent residential building. The rich findings (including the Polydus mosaic) prove the use of the building until the second half of the 3rd century.

According to its original conception, the resulting thermal complex is one of the largest buildings of its kind in the Roman Empire; only the urban Roman thermal complexes of the emperors Trajan, Caracalla and Diocletian were larger. The ground plan corresponds to the so-called small imperial type, which is, however, already familiar from the older Baths of Barbara.

However, the Imperial Baths were never actually put into operation. Probably already with the transfer of the residence to the east after 324 the work on it stopped, although large parts of the construction were already completed beyond the first floor. It was not until Valentinian I chose Trier as his residence again that work was resumed, but with a completely different conception. The already completed bathing facilities were removed and the western part with the frigidarium was demolished. The circular hall of the tepidarium was used as an entrance hall, and the palaestra was significantly enlarged and transformed into a paved square. Interpretations vary between residential palace, imperial forum and – most likely in the opinion of the excavator – barracks for the imperial bodyguard (scholae palatinae). In the Middle Ages, large parts of the complex were integrated into the city's fortifications, preserving, for example, the eastern facade, which is over 20 meters high.^[77]

Constantine Basilica

Main article: Aula Palatina

Reconstruction of the shop front with the main entrance

Although the name and appearance of today's Constantine(s) Basilica seem to refer to an ancient church building, the structure was originally built as the reception hall of the imperial residence. The frequently used name Palastaula or Aula Palatina is more accurate, but is unattested in classical Latin.^[78] The basilica has a length of 69.8 m (including the 12.4 m long apse) with a width of 27.2 m.^[79] In antiquity, it possessed a height of about 30 m. The exterior is 2.7 m thick. The 2.7 m thick exterior walls were of brick masonry and plastered on the outside. Parts made of red sandstone are modern additions.

View of Palastaula from the west

The interior had a quality wall covering: The nave and apse had flooring and wall paneling of inlaid marble slabs (opus sectile) up to the height of the uppermost window cornices, of which remnants and especially the holes of the iron brackets have survived. Above this followed stucco work up to the cantilevered ceiling, which may not have been dissimilar to the present coffered ceiling inserted in 1955. Remarkable are the heating systems, through which the 1600 m² interior was heatable via a three-part hypocaust with five praefurnia. The basilica was not a stand-alone building in ancient times. In the south, in front of the main entrance, there was a porch also covered with marble, and on the outside there were porticoes with courtyards leaned against them. The remains of these buildings are either preserved or marked in the pavement of the present square.

The Palastaula was probably erected as a representative building in the years 305–311 when it was converted into a residence.^[80] The monumental building served as a backdrop for audiences, receptions and court ceremonial, with the emperor's throne assumed to be in the apse. Considerable leveling was required for the large structure, which also covered a street intersection. The western block previously housed the official residence of a high imperial official.

After the end of Roman rule, the burnt-out building was added to the Frankish royal estate. In 902 the ruins were donated to the Bishop of Trier. Subsequently, the basilica was rebuilt into a castle-like complex, the apse was closed to the tower, while in the walled interior of the church economic and cellar buildings were created. After 1614, the south and east walls were demolished and the masonry was integrated into the new Electoral Palace or used as a courtyard. After being plundered by French Revolutionary troops in 1794, the complex served as barracks and a military hospital. In 1844, Prussian King Frederick William IV ordered its reconstruction as a place of worship for Trier's Protestant community. During the Second World War, the palace and basilica were severely destroyed. Reconstruction could not be started until 1954, allowing excavations and accurate recordings of the building fabric.^[81]

Cathedral

Main article: Trier Cathedral

The transition of the city from Late Antiquity to the Middle Ages can be seen in the cathedral as the nucleus of

Domstein in Trier

Giant column in the late Roman quarry at Felsberg in the Odenwald forest

medieval Trier. Accordingly, it has been archaeologically explored since 1843. Larger excavations took place after the Second World War until 1981; they established as the oldest layer a noble Roman residential quarter of the 2nd and 3rd centuries AD. This included a state hall richly decorated with wall and ceiling paintings.^[82] Parts of the building are preserved under the crossing of the cathedral, and the reconstructed frescoes are exhibited in the Cathedral and Diocesan Museum. The rich decoration has led to the fact that the complex is partly attributed to a late antique palace building.

The residential buildings were demolished and leveled in the early 4th century. A double church complex with two east-facing, three-aisled basilicas was built. The columns of the north basilica were made of Odenwald granite,^[83] which was transported here from the Felsenmeer near Lautertal via the Rhine and Moselle rivers. The cathedral stone lying in front of the cathedral still indicates this. The width of the two church complexes, including the transverse buildings and peristyle courtyards, was probably between 40 (north basilica) and 30 meters (south basilica below today's Liebfrauenkirche), with a length of 150 meters each. Between the two churches there was a square baptistery, which is marked today in the paving of the cathedral courtyard. After a destruction towards the end of the fourth century, the northern basilica was rebuilt and a square building with a side length of 41.5 m was erected in the area of the crossing. Along Windstrasse on the north side of the cathedral, the associated brickwork is still visible to a height of 30 m.^[84]

Cemeteries

The cemeteries of the Middle Imperial Period have only been partially explored and their extent is largely unknown. In the earliest phase of settlement until around the middle of the 2nd century, smaller necropolises close to the settlement were established near the Moselle and along the Olewiger Straße towards the amphitheater. With the construction of the city wall these cemeteries had to be abandoned. The cemeteries to the south and north of the city were relocated, so that some earlier burials were also discovered within the later walled area. The usual form of burial at this time was cremation. Corpse burials do not appear until the 2nd century, sarcophagi are attested from the middle of the 2nd century.

After the construction of the city wall, the largest necropolises were located along the northern and southern arterial roads. In the northern cemetery, burials were initially concentrated along the road that ran slightly west of today's Paulinstraße. After the draining of an old arm of the Moselle, this area could also be used for burials up to today's Steinhausenstraße, so that burials of the 4th century in particular are found here. The southern burial ground extended along today's Matthiasstraße. From the middle imperial period more than 2000 inventories of cremation burials have come to the State Museum.^[85] Later sarcophagus burials were concentrated under the church there, in the northwest the cemetery was bordered by the pottery district.

Sarcophagi of Bishops Eucharius and Valerius in St. Matthias

East of the city in front of the city wall north of the amphitheater cremation and inhumation graves were found, which are today built over. A cemetery with body burials of the 3rd and 4th centuries is located on the slope above the amphitheater. Rich grave goods of glass and ceramic vessels are known from this cemetery. On the western bank of the Moselle were cemeteries in the present-day districts of Trier-West/Pallien and Euren along the road leading to Reims.^[86]

The above-ground design of the graves could be very different. Stone monuments from the associated grave streets are known in the Trier region especially with the Neumagen stone monuments and the Igel column. Particularly wealthy people occasionally had underground burial chambers with a temple building above built, as they were preserved for example at the West Cemetery, with the burial chamber at the Reichertsberg or the Grutenhäuschen. It is not certain whether the so-called Franzensknüppchen on the Petrisberg above Trier is a monumental burial tumulus.

In late antiquity, tombs were concentrated at the burial places of saints, bishops and martyrs. Medieval churches developed from these burial chapels located outside the city walls. A parallel development can be traced in many late Roman cities; in Trier it can be grasped in three places with the late Roman tombs under the Paulinus Church, the St. Matthias' Abbey and the St. Maximin's Abbey.^[87]

Surrounding area

Already in the middle imperial period, larger Villa Rustica were built in the surrounding area of the city, which profited from the short distances to the markets and were therefore – as in the immediate vicinity of many Roman cities – significantly larger. Examples of such complexes can be found in Mehring and Villa Otrang. While at the time of their foundation the complexes were still designed for agriculture and cattle breeding, vineyards increased considerably in the course of the 3rd and 4th centuries. In many complexes a larger wine press house was added at this time. This may be related to the presence of the imperial court.^[88] However, Emperor Probus is also said to have issued a provision at the end of the 3rd century lifting old restrictions on vine cultivation in the provinces.^[89]

The presence of the imperial administration led to the fact that some of these complexes were particularly magnificently expanded or monumental complexes were newly built in the 4th century. An outstanding example is the Villa von Welschbillig, in front of whose main front there was a large water basin with originally 112 herms. Its location in the area of the long wall indicates an imperial domain. Similar functions are also assumed for the important late antique palace complexes of Konz (Kaiservilla von Konz) and Trier-Pfalzel (Palatiolum).^[90]

The oldest Roman road in the region is considered to be the connection from Lyon via Metz to Trier, which was laid out by Agrippa.^[91] The road, which was well preserved in places, continued as the Roman road from Trier to Cologne across the Eifel to the Rhine. The best known Roman road to Trier is the Ausonius Road, named after the Roman poet and statesman Ausonius, who was active in Treveris for a long time. It ran over the Hunsrück to Bingium, where it reached the Roman Rhine Valley Road. Further road connections led, among others, via Coriovallum (Heerlen in the Netherlands) to Colonia Ulpia Traiana (near Xanten), to Strasbourg and along the Moselle to Koblenz (Confluentes). In late antiquity, these roads had to be additionally protected with fortifications, for example at Neumagen, Bitburg and Jünkerath.