These aqueducts, which supplied the fountains in the Trastevere, all come from the lakes on the hills. The Alsietina of Augustus comes from the lake of that name (now called Martignano), between the Via Claudia and the Via Aurelia, but not very near to either, being 6½ miles from the Via Claudia at the fourteenth milestone, as Frontinus states. This was made to supply the Naumachia of Augustus, which were near the present monastery of S. Cosimato in Trastevere; the water was very abundant, but not fit for drinking. It entered Rome at a lower level than any of the other aqueducts, because the Naumachia were very little above the level of the Tiber. At the small town called the Cariæ (near the present Osteria Nuova), about fifteen miles from Rome, it received an additional supply of water from the Lacus Sabatinus. Trajan restored to use that part which came from the latter lake; this is better water than the Alsietina. Pope Paul III., A.D. 1540, again restored this to use, and it is now called Aqua Paola. His engineers brought the water from three lakes, the two before mentioned, and a smaller one above the Alsietina, called Stracciacappe. The object of bringing the water from this very high level, 500 ft. above Rome, was to supply the splendid fountains in front of S. Peter’s, the water of which rises to a great height. This lake was drained in 1870, and at the same time the water in the Alsietina was also much lowered, by which means the three _specus_ were brought to light on the bank, and the sites are shewn on this map. The Aqueduct of Trajan was carried at a much higher level than that of Augustus, and entered Rome on the top of the Janiculum. Procopius, in the sixth century, admired the profuse supply of water at that point; and the water was then, as it is now, used for a series of mills on the slope of the hill. The engineers of Pope Paul made use of the water of all the three lakes, and a most abundant supply still flows into Rome through the Fountain, above the Church of S. Pietro in Montorio. How far the old _specus_ was used it is difficult to tell, but most probably that of Trajan was used for a large part of the distance; it is almost entirely underground until the last mile into Rome, where it was carried on an arcade of the time of Trajan. The Aqua Paola is there also carried on an arcade, parallel to it and near to it, but not the same. FOOTNOTES