Note 39 — Chapter IV · PART I. THE AQUEDUCTS.

This castellum aquæ is exactly two miles from the Porta Maggiore, another proof that the entrance to Rome (though not to the City) was considered by Frontinus to have been at that gate. All the aqueducts on the eastern side of Rome are measured by him from this gate, and the inscriptions put over that gate as the entrance into Rome indicate the same thing. The level of this castellum above the sea is about 153 ft.; at the Porta Maggiore, where the Anio Vetus enters Rome, it is about 146 ft., allowing a descent of about 3 ft. 4 in. for the two miles, which is natural. The Via Appia Nova, in the part near Rome, was made out of the old Via Asinaria. Frontinus says that this branch “was conveyed to the Asinian gardens,” which were between the Lateran and the Sessorium, and to which the Porta Asinaria (or gate of the Asinii) was the entrance. Between that gate and the Amphitheatrum Castrense are remains of an ancient reservoir or castellum aquæ, cut in the rock at the foot of the wall and half underground, as was very usual with the Anio Vetus. The branch that goes along the Via Latina appears to have gone from the same reservoir, but to be distinct from the one mentioned by Frontinus, and to have been made after his time. This last branch seems to be the same as the Aqua Antoniniana of the Regionary Catalogue, having been made in the third century to supply the great Thermæ of the Antonines. In the Middle Ages, this was considered to have been a branch of the Aqua Marcia; but if this had been the case, there must have been some remains of the arcade for it across the valley.