I Montium et Biberatice

By the 12th century, the older 10th century region of Biveretica had its name changed to Montium et Biberatice, before simply becoming Montium at the close of the 14th century. This change of name reflected the fact that the Esquiline and the Viminal Hills, and parts of the Quirinal and the Caelian Hills belonged to this rione during the Middle Ages. Like many of the regions during the Middle Ages, the parts on top of the hills were abandoned, as the population sought to remain close to the Tiber River, and so only the part of the region that contained the easternmost part of the Campus Martius was inhabited.

By 1143 this region also contained the Forum Romanum and the Colosseum, which was not a part of the older Montium et Biberatice. The Colosseum had at some point during the Middle Ages been fortified and for a time belonged to the area controlled by the Frangipani family.

In the beginning of the 16th century this region included part of the district in the neighbourhood of Forum of Trajan, and by the 19th century, the region then referred to as Monti had a boundary which passed between Trajan's Forum and the Santi Apostoli.

II Trivii et Vie Late

A region that is believed took its name from absorbing part of the Via Lata, the old Seventh Region of Augustan Rome, while the Trivii described the three principal streets that led to the "piazza dei Crociferi", a square next to the modern Trevi square. The importance of this location in Medieval Rome is that it was the main output for the Aqua Virgo aqueduct, one of the few aqueducts which underwent frequent restoration works during the centuries. By its remaining active it enabled the region to survive well throughout the Middle Ages, although the change of its sources caused the water's properties (purity, taste, etc.) to become much worse than the original one, which was only restored during alteration works in 1562.

During the Middle Ages, the higher reaches of the region (which included part of the Quirinal Hill) were abandoned, as the people chose to inhabit the parts of the region closer to the Tiber River, and during the 9th century, this region was the aristocratic quarter of Rome.^[5] Its name was transformed in modern times to become the region of Trevi.

III Columpne et S. Marie in Aquiro

This region included parts of the city situated around its most prominent features, the Column of Marcus Aurelius, or Antonine Column (late 2nd century), now standing in Piazza Colonna and the Church of Santa Maria in Aquiro. It also contains the remains of the Temple of Hadrian, with its eleven columns also contributing to the name of the region. A prominent feature during the Middle Ages was the Mons Acceptorius, a small artificial embankment created by the pre-Roman inhabitants in order to drive stilts into the swampy ground, and build dry huts for housing. Prior to the 16th century, the region was never densely populated. It now forms part of the modern rione of Colonna.

IV Campi Martis et S. Laurentii in Lucina

Included the parts of Rome around the Campo Marzio and San Lorenzo in Lucina.

V Pontis et Scorteclariorum

Included the parts of Rome around Ponte. Unlike its modern counterpart, it included the area across the Tiber spanned by the Ponte Sant'Angelo. This bridge was built by Emperor Hadrian (and originally named after him Pons Aelius) in 134 to connect his mausoleum to the rest of the city.

In ancient Rome, the area belonged to the IX Augustan region called Circus Flaminius, that was a part of the Campus Martius. Nero built another bridge, that was called Neronianus or triumphalis because the Via Triumphalis, the Triumphal Way, passed over it: Starting with Titus, the victorious Emperors celebrating their Triumphs entered Rome marching through it.

Nero's bridge was also called Pons Vaticanus (meaning "Vatican Bridge" in Latin), because it connected the Ager Vaticanus to the left bank, later Pons ruptus ("broken bridge"), because it was already broken in the Middle Ages.

Pope Sixtus V eventually changed the rione limits so that the Ponte Sant'Angelo belonged to Borgo.

VI S. Eustachii et Vinea Teudemarii

Included the parts of Rome around the church of Sant'Eustachio and forms part of the modern rione of Sant'Eustachio.

VII Arenule et Caccabariorum

The name of the region stemmed from Arenula, (the name is present in the modern Via Arenula) that was the name given to the soft sand (rena in Italian) that the river Tiber left after the floods, and that built strands on the left bank. It included parts of the city around Regola.

In Augustan Rome, the medieval region straddled both the Campus Martius and the IX region called Circus Flaminius. Here there was the Trigarium, the stadium where the riders of the triga (a cart with three horses) used to train. During the early Middle Ages, it belonged to the 4th of the seven ecclesiastic regions.

The region was not widely inhabited due to the frequent flooding of the river Tiber, causing the whole area to be extremely unhealthy, especially during summer. It was only drained at the end of the Middle Ages, after which it was reclaimed by the city and reinhabited once again.

VIII Parionis et S. Laurentii in Damaso

During Antiquity, it belonged to the 9th Augustan region called Circo Flaminio. In this area Pompey built his curia, while Domitian built his stadium and an Odeon (Odeum in Latin), for musical and poetic competitions. During the early Middle Ages it included parts of the city around San Lorenzo in Damaso. From 1200 the population kept on increasing until the 15th century, when it increased in importance due to the paving of Campo de' Fiori, so that it soon became an important economic center.

Under Sixtus IV (1471–1484) the rione lost much of its chaotic look, typical of the Middle Ages, for a cleaner and tidier one, in keeping with the changes brought about by the Renaissance. It saw the recovery of buildings, the enlargement of streets, and the rebuilding of the ancient Pons Aurelius into a new bridge, the "Ponte Sisto" connecting Trastevere and Parione. This activity improved the quality of the region.

Thanks to this renewal, urbanization increased between the 1400 and 1500. In the same period, several artists were asked to renew the front of the most important of the buildings in the region. In 1500, most of the commercial activity slowly moved from Campo de' Fiori to Piazza Navona, due to the fact that it had more space for trading.

Today it is part of the modern rione of Parione.

IX Pinee et S. Marci

At the beginning of the 10th century, this region was referred to as Pina before transforming into Pinee et S. Marci by the 12th century, and finally into Pigna by the 16th century. For many centuries this region has been reckoned as the ninth region, certainly parts of it, such as the Pantheon were included in the ninth region of Augustan Rome.

From at least the 16th century, and possibly much earlier, this region has been centered on the Basilica of San Marco, Santa Maria sopra Minerva and the Pantheon.

X S. Angeli in Foro Piscium

The Theatre of Marcellus, after which a region of Rome was named in the 10th century.

Referred to as Regione Marcello in the tenth century, by the 12th century, its name had changed to indicate that it included parts of the city around the fish market, which had moved from the Forum Piscarium, located near the Forum Romanum, into the ruins of the Porticus Octaviae, though it still included the Theatre of Marcellus, which now housed the shops of smiths and coppersmiths inside the arcades of the theater.

It also included the most important church of the rione, Sant'Angelo in Foro Piscium ("St. Angel in the Fish Market"). This church, erected in 770 inside the Propylea of the Portico of Octavia, had a great historical importance during the Middle Ages. From here, on the Whitsunday of 1347, the Romans, led by Cola di Rienzo, launched the assault on the Capitol, attempting to restore the Roman Republic.

This region now forms part of the region of Sant'Angelo.

XI Ripe et Marmorate

Includes part of the city that bounded on the east bank of the old Port of Rome, the Ripa Grande ("Great Bank"), it was constructed after the Second Punic War, and was only abandoned in the 19th century. The area of the Marmorate referred to the river bank south of the Aventine Hill where, since the imperial age, rough blocks of different kinds of marble (marmora), shipped to Rome from the East, were stored in a large deposit area, called the emporium.

During the period of the high empire, a number of rich mansions stood here but they were mostly destroyed during the barbarian invasions of the 5th century, resulting in the area being almost completely abandoned, with the exception of a few convents on the heights of the Aventine Hill, located on a safer spot. The district became again inhabited during the Renaissance, when sometime during the 16th century the river port called Ripa Grande was made operational once again.

During the 13th century, the section where the Arch of Janus is located was included by the Frangipani family in their fortified estate, which stretched over the Palatine Hill and included the remains of the small Frangipani Tower at the southern end of the Circus Maximus, which was also within this region. The area also had the headquarters of the Knights Templar in Rome from the 11th to the 13th centuries.

The region incorporated parts of today’s Via Marmorata, and forms part of the modern rione of Ripa.

XII Campitelli et S. Adriani

During the 10th century, this region was referred to as the Clivus Argentarii, and it contained the streets that now connect the Corso with the Forum Romanum (the old Via di Marforio). It includes parts of the city around the Piazza di Campitelli, near Santa Maria in Campitelli, and forms part of the modern rione of Campitelli. It also included the church of Sant'Adriano al Foro.

XIII Trastevere

Originally a separate region in 1143 from the Tiber Island, these two regions were combined in the 13th century, bringing the total number of regions down to thirteen.

XIV Insula Tiberina

The Tiber Island. After its amalgamation with the region of Trastevere, Rome did not get a fourteenth region until 1586 when Sixtus V added the old Leonine City, considered until then outside the city, as a new administrative division, under the name of Borgo.