Hellenistic precursor and Herodian pool

Lying at the foot of the rock scarp that once bore the Antonia Fortress, the pool is located at the northwestern corner of Jerusalem's Temple Mount. Measuring 52 by 14 metres, the pool is oriented from northwest to southeast, with its depth increasing from 4.5 metres in the north to 6 metres in the south. The pool's long eastern and western walls are not horizontal but also drop steadily to the south. Once open-aired, the pool was accessible along both long walls by a series of rock-cut steps covered by waterproof mortar composed of chalk and ashes.^[2]

The pool was apparently built by Herod the Great during his construction of the Antonia and the renovation of the Temple Mount in the late first century BCE. The only pool known to stand in close association with the site of the Antonia, there is little doubt that it was constructed no later than the fashioning of the rock scarp above it, as the orientation of the pool conditioned a slight directional change in the rock podium's northeastern corner. It is therefore identified with the Struthius or Struthion ('sparrow') pool mentioned by Josephus in his description of Titus' siege of the Antonia during the Great Revolt (70 CE):^[2]

For there were now four great banks raised, one of which was at the tower Antonia; this was raised by the fifth legion, over against the middle of that pool which was called Struthius

— Josephus, The Jewish War V. 467^[3]

The discovery of Seleucid and Hasmonean coins in the debris of the pool, as well as the similarity between local mortar and mortar used in other Hasmonean cisterns and baths in Jerusalem, may suggest a pre-Herodian origin to the pool. The Struthion is also accessible by a rock-cut passage that leads south for 34 meters before reaching the western wall of the Temple Mount enclosure. Blocked by the Herodian construction, this was an earlier aqueduct that once fed one of the cisterns underneath the Temple Mount enclosure itself. The aqueduct has been attributed to the Hasmoneans, though an earlier Ptolemaic association cannot be ruled out. With a floor 3 meters above the top of the pool, this passage would have remained dry at the time the pool was in use and may have been used as a secret means of access to the pool from the fortress or Temple Mount. Another passage exists north of the pool, though its relation to the pool or the southern passage is unknown.^[2]

Late Roman vaults and pavement

Once open-aired, the pool was later covered by two longitudinal barrel vaults that spring from the side walls and connect on a wall running along the center of the pool pierced by a series of arches. This division is the source of another name given to the Struthion, the Twin Pools. The two vaults were built to support a large flagstone pavement that covered the area above the pool. This pavement features shallow channels that carried runoff water into the pool as well as masonry manholes.^[2]

Opinions differ as to the dating and origin of the pavement. Originally thought to be contemporary with the construction of the pool and thus to belong to the Antonia Fortress, reexamination of archaeological data by Father Pierre Benoit has prompted a revision of its dating. The vaults and pavement are rather thought to be contemporary with the nearby Ecce homo arch, originally a triumphal arch constructed by Emperor Hadrian, and thus assigned to the 2nd century CE. This reasoning seems to be supported by Josephus' account of the siege of the Antonia, although whether Josephus had meant a ramp had been built in, over or opposite the middle of the pool remains unclear.^[2]