The Marcia was begun in 144 B.C. by the praetor Q. Marcius Rex, who had been ordered by the senate to repair the two existing aqueducts, Appia and Anio, and to build a third, as the supply of water was insufficient. The completion of the Marcia required five years, and the water was successfully brought to the top of the Capitoline in 140 B.C.
This was the first of the high-level aqueducts, its source being about 275 metres above Rome in the Sabine mountains. This source was two or three--perhaps those known as the second and third Serena--of a series of eight springs which extend along the north side of the Anio, between Arsoli and Agosta, at the base of monte della Prugna and near the thirty-sixth milestone of the via Valeria. The water of all these springs is remarkably clear and cold, and the water of the aqua Marcia was the best brought into Rome in antiquity.
The course of the Marcia can be traced from its source to Gallicano, as it winds down the hills, following the Anio to Tivoli, and then bending to the south, crossing the valleys on bridges and passing through the hills in tunnels. This part of its course is practically the same as that of the Anio vetus, the Claudia and the Anio novus. At one point a single bridge, the ponte Lupo, carries all four. From Gallicano the Marcia ran underground to the sixth milestone on the via Latina, and thence to the porta Praenestina on arches which continued to the porta Tiburtiua (porta S. Lorenzo), and to the distributing station on the Viminal.
The later aqueducts, Julia and Tepula, ran on these same arches as far as the porta Tiburtina, above the specus of the Marcia, and the stretch between this gate and the porta Praenestina was afterward incorporated into the Aurelian wall. Where these arches began at Roma Vecchia, their ruins are still visible.
Within the city the Marcia was carried in pipes from the Viminal to the Capitoline, and above ground to the Caelian. During the reign of Nero, a branch called the rivus Herculaneus was built, which ran underground from the main aqueduct, a little south of the porta Tiburtina, across the Caelian to the porta Capena. In the villa Wolkonsky some remains of an aqueduct have been found, consisting of tufa blocks pierced with a circular channel, which probably belonged to this branch. This was extended by Trajan to the Aventine. In 212 A.D. Caracalla built another branch, the aqua Antoniniana, nearly kilometres long, from a point near the porta Furba (3 kilometres from the porta S. Giovanni), to carry water to his baths. This crossed the via Appia on the so-called arch of Drusus, and near by are ruins of other arches. In 284 A.D. Diocletian restored the Marcia; and afterward the name Iovia was applied either to the whole aqueduct, or to the branch Antoniniana.
Augustus increased the volume of water of the Marcia by building a short branch from its head to another spring about 1200 metres farther from Eome. This additional supply was for use in time of drought, and could be turned into the Claudia instead of the Marcia, if necessary. The total length of the Marcia was 91.3 kilometres. Its specus was under- ground from its source to the point where it emerged at Roma Vecchia, except at a few places where it was carried across valleys on arches.