Aqua Claudia ("the Claudian water") was an ancient Roman aqueduct that, like the Aqua Anio Novus, was begun by Emperor Caligula (37–41 AD) in 38 AD and finished by Emperor Claudius (41–54 AD) in 52 AD. It was the eighth aqueduct to supply Rome and together with Aqua Anio Novus, Aqua Anio Vetus and Aqua Marcia, it is regarded as one of the "four great aqueducts of Rome". Route Its mainsprings, the Caeruleus and Curtius, were situated 300 paces to the left of the 38th milestone of the Via Sublacensis. The total length was approximately , most of which was underground. The flow was about in 24 hours (about ). Directly after its filtering tank, near the seventh mile of the Via Latina, it finally emerged onto arches, which increase in height as the ground falls toward the city, reaching over . It is one of the two ancient aqueducts that flowed through the Porta Maggiore, the other being the Aqua Anio Novus. It is described in some detail by Frontinus in his work published in the later 1st century, De aquaeductu. Nero extended the aqueduct with the Arcus Neroniani to the Caelian hill and Domitian further extended it to the Palatine, after which the Aqua Claudia could provide all 14 Roman districts with water. The section on the Caelian hill was called arcus Caelimontani. Bridges Visible remaining bridges include the Ponte sul Fosso della Noce, Ponte San Antonio, Ponte delle Forme Rotte, Ponte dell`Inferno, Ponte Barucelli. Ponte dell`Inferno The bridge has a single arch in opus quadratum, reinforced in the late period in brickwork. The specus (channel) is about 1 m wide and is also built in opus quadratum, but with a very porous stone which is locally found as a layer immediately above the tuff on which the bridge rests. Ponte Barucelli The Ponte Barucelli (also known as Ponte Diruto) is made up of two monumental bridges 8 m apart for the aqua Claudia (to the north) the Anio Novus (to the south) to cross the Acqua Nera stream. Both date to between 38 and 52 AD. They were later strengthened with buttresses and reinforcements, becoming two huge continuous and connected structures. The Anio Novus bridge, about 85 m long and about 10 m wide, has a few small arches except for the main high and narrow one for the Acqua Nera. It had originally been built of