tuff in opus quadratum. In the second half of the 1st century it was reinforced in opus mixtum, visible at the two east end buttresses. At the beginning of the 3rd century nine rectangular buttresses were added at regular intervals on the north side while on the south side only three were added near the bed of the stream, later increased by five on the west bank in poor opus latericium and two on the east in opus mixtum. Later the two bridges were connected by three brick arches and with buttresses. Repairs The aqueduct went through at least two major repairs. Tacitus suggests that the aqueduct was in use by AD 47. An inscription from Vespasian suggests that Aqua Claudia was used for ten years, then failed and was out of use for nine years. The first repair was done by Emperor Vespasian in 71 AD; it was repaired again in 81 AD by Emperor Titus. Alexander Severus reinforced the arches of Nero (CIL VI.1259) where they are called arcus Caelimontani, including the line of arches across the valley between the Caelian and the Palatine. The church of San Tommaso in Formis was later built into the side of the aqueduct. Gallery See also List of aqueducts in the city of Rome List of aqueducts in the Roman Empire List of Roman aqueducts by date Ancient Roman engineering Ancient Roman technology Notes External links Interactive map with the full Aqua Claudia Map of Rome with Aqua Claudia running (red) The Aqua Claudia Webpage 3D digital model of Rome featuring Aqua Claudia Buildings and structures completed in the 1st century Claudia 50s establishments in the Roman Empire 1st-century establishments in Italy Claudius Caligula 52 establishments