The Reservoirs of this most ancient and very deep aqueduct were first in the quarries before mentioned, and even in Rome were chiefly also in quarries, as at the mouth; but just within the Porta Maggiore, and close to the gardens of S. Croce, formerly the Sessorian Palace, are two large reservoirs very near together, supposed to have been the Gemelli or twin reservoirs mentioned by Frontinus, and these are so deep that they appear to have belonged to the Aqua Appia. Some excavations attempted in them in 1867 were stopped by water (410, 411, 695*). This aqueduct is believed to have entered Rome on the northern side of these gardens, and to have been first received in the reservoir afterwards called after S. Helena, which is very deep, and in this situation (546). II. ANIO VETUS, MADE IN THE YEAR OF ROME 481, B.C. 272.[221] The Anio Vetus and the Anio Novus are in fact branches of the river Anio, which falls into the Tiber a short distance above Rome. The water is there seen to be much more pure than that of the Tiber, and after it falls into the muddy Tiber its clear water can be distinguished for a long distance. Several of the aqueducts, as the Appia and the Virgo, are springs, that fell into that river; but part of the water was intercepted and brought into Rome, each in its own distinct _specus_. This was the case with the Anio Vetus, at a much higher level above Tivoli, but below Subiaco. The river itself may be considered to belong to the system of the Aqueducts, and the series of magnificent cascades by which it falls from its high level, are partly artificial, are connected with them, and illustrate their history. Those in Tivoli (1545, 1546, 1547, 1548), the engineers had great difficulty in avoiding. The one near Vico-Varo (1544), above Tivoli, is near the point from which the aqueduct was taken, which is near the valley called Arsoli (1549). It can be seen in the valley of the Arches, two miles above Tivoli, at the foot of one of the piers of the Marcian Arcade (1054), and the one seems to have followed the other all the way into Rome. It passes along with it over the Ponte di S. Antonio, which is one of the finest bridges on the whole line of the Aqueducts, eight miles below Tivoli, across the valley and mountain stream called S. Antonio (1530). This aqueduct can generally be distinguished by being half-underground, or very near the surface. It was repaired or restored by Augustus and Trajan[222], and most of the remains now visible are of their time, and both the _specus_ and the _castella_ can generally be known by being faced with _opus reticulatum_, so much used at that time. There is a fine reservoir or _castellum_ for it near Tivoli, with very peculiar work of this description, and extremely picturesque (950). Another is against a bank, and half underground, near the Torre Fiscale, three miles from Rome, and close to the foot of the Claudian Arcade (896, 1028, 1029). Remains of others may still be seen