The line of this aqueduct, which is chiefly subterranean, can be traced backwards by the respirators of Paul V., who repaired it, from his fountain on the Janiculum in Rome across Monte Mario to La Storta, and a little beyond it to the junction of the roads from Viterbo and Bracciano. Here the present road follows a winding course for the sake of better gradients, but the old one (_Clodia_) followed a more direct line in a cutting through the hill, to the left of the present road, as may be seen by the old paving-stones at intervals; and here, instead of the clumsy respirators of Paul V., are wells only, one of which is near the present road at the junction. The respirators are built over old wells, and serve to shew that Paul V. restored the _specus_ from La Storta to Rome only in this part. There are no respirators beyond that point for some distance, but the _specus_ may still be traced by the wells descending into it. About two miles further on, this _specus_ is carried on an arcade across a valley, and it may be traced from thence to the point where Nibby explored it in 1826, near the lake of Bracciano. From the Osteria Nuova (fifteen miles from Rome) to La Storta (ten miles from Rome), the rough pyramids continue along the line of the aqueduct, and at the Osteria itself there are two of different dimensions close together at the end of the house or _castellum aquæ_; one is nearly double the size of the other, and both are of very rough construction. Probably one of these is of the time of Trajan, the other of the time of Pope Paul; these wells, with the smaller pyramids over them, are continued to near La Storta; here a change takes place, and the respirators are modern, as has been said. Procopius expresses his amazement at the quantity of water thus brought to the top of the Janiculum, and poured in torrents over the whole of the region of the Trastevere. This is still the case, and the fountains in front of St. Peter’s and in the gardens of the Vatican, are also supplied from this aqueduct. The water is so abundant that it is even brought over the bridge and supplies a fountain on the other side.