The Aqua Claudia built by Emperors Caligula and Claudius brought water to Rome from Subiaco, 45 miles away. The main water sources were the Caeruleus and the Curtius, two springs situated 300 paces to the left of the thirty-eighth milestone of the via Sublacensis, which was only 100 paces from those of the Aqua Marcia. Part of its length is on solid masonry but for 9.5 miles it is borne on lofty arches, great lengths of which remain in the Campagna. It is probably the finest of all Roman aqueducts with some of its arches over 100 feet high. Three miles from Rome it is joined by the Anio Novus, 62 miles in length.

Click here to see a map of the Aqua Claudia, 38-52 CE, named after the emperor Claudius.

Generally speaking, aqueducts are extraordinarily striking features in the Roman landscape. They carried immense quantities of water required for the great thermae and public fountains, to say nothing of the domestic requirements of a large population. It has been calculated that 350,000,000 gallons of water poured daily into Rome through her eleven great aqueducts.

In the days of Imperial Rome one of the most impressive sights in the Campagna was the long, level flights of lofty arches that are the aqueducts of Rome. No more imposing triumphal procession ever entered Rome than that of her aqueducts, majestically bearing captive waters from distant hills, and no greater manifestation of the adoption of simple means to supply a need of everyday life is anywhere to be seen than in these water-carrying arches.

From LacusCurtius:

The Aqua Claudia (like the Anio Novus, q.v.) was begun by Caligula in 38 A.D. (Suet. Cal. 21), and completed by Claudius anywhere between 47 and 52. After being in use for only ten years, the water supply failed and was interrupted for nine years until Vespasian restored it in 71. Ten years later Titus had to repair it once more - 'aquas Curtiam et Caeruleam ... cum a capite aquarum a solo vetustate (!) dilapsae essent nova forma reducendas sua impensa curavit.' In 88 a tunnel under the mons Aeflanus near the Tiber was completed. There are no records of other restorations except from study of the remains themselves, which show that a good deal of repairing was done in the second and third centuries.

The length of its channel is given in the inscription on the porta Maior as 45 miles, while Frontinus gives it as 1 mile 406 paces more, which is probably to be accounted for by his measuring up as far as the fons Albudinus, which was added between the time of Claudius and his own. Pliny's figure (40 miles) is only an approximate.

The Emperor Domitian extended the Aqua Claudia up to the Palatine to supply the palace with water.

The fons Augustae (see Aqua Marcia) was also turned into the Aqua Claudia when the Marcia was full; but sometimes even the Claudia could not carry it, and it ran to waste (Frontinus ii.72). The source springs are slightly further up the Anio valley than those of the Marcia, but belong to the same group. Volume at the springs was 4607 quinariae, or 191,190 cubic metres in 24 hours. The course outside the city cannot be confirmed. Directly after its piscina, near mile seven of the via Latina, it finally emerged onto arches that increased in height as the ground fell towards the city. Also carried along was the channel of the Anio Novus (q.v.), the highest of all the aqueducts. Both channels still pass over the Via Labicana and Via Praenestina by a great monumental arch, which later became the Porta Maior (q.v.).

The Aqua Claudia winds amid the mansions of the Cælian Hill.

From the Porta Maior the Arcus Caelimontani (q.v.) diverged to the left and conveyed a portion of its supply across the Caelian to the Palatine, the Aventine and the Transtiberine regions (Frontinus, i.20). That this branch also supplied the first region is clear from CIL VI.3866 =31963, which mentions a castellum situated in it.

The main aqueduct ran on to the terminal piscina post hortos Pallantianos; it must also have supplied the higher parts of the city, the Esquiline, Viminal and Quirinal, which, as Pliny says, its height enabled it to do. See references under Anio Novus, and also Mél. 1906, 305‑311; CIL VI.8494. The Forma Claudiana is mentioned in Eins. 7.18, 19 (where the actual aqueduct is referred to; see also Aqua Iulia, Arcus Neroniani). Forma Claudia is found as one of the boundaries of a vineyard near Porta Maggiore in a document of 1066 (Reg. Subl. No. 104, p150; cf. HCh 296).

Detail of the Aqua Claudia going through the Cælian Hill.


Sources:
Les Maquettes Jacques Plassard
LacusCurtius
Aquaeducts
Roman Architecture