Aqua Virgo
The aqueduct ran underground for nearly all of its 20.5 km (12.7 mi) length[1]: 28 except the last stretch of 1,800 m (5,900 ft) running partly on arches in the Campus Martius area, of which two sections remain.
It ran along via Collatina up to the Portonaccio area, passed via Nomentana to via Salaria, and then turned south and entered the city under the Horti Lucullani and crossed 1.2 kilometres (0.75 mi) to the area of the Pincian Hill and current Villa Medici, where a spiral staircase (called the Pincio snail) leads to the underground conduit.
After the limaria pool (settling basin) near the Pincian, the urban stretch began partially on arches, many discovered in 1871.
Later interpretation has found that the aqueduct’s arches continued along the Via del Seminario to a point east of the Pantheon.
A secondary branch reached the inadequately served regions VII, IX, and XIV in the Trastevere area.
The route passed from the low area of the Campus Martius over the higher ground of the ridge surrounding the Pantheon basin, and then over the bridge of Agrippa.
Emperor Claudius renovated it in 46 AD, as witnessed by an inscription on the architrave in via del Nazzareno, which states that he rebuilt large sections of the aqueduct at this point because Caligula had removed stone for use in constructing an amphitheatre[citation needed].
In the 1930s, a pressurised version was built, the Acqua Vergine Nuovo, separate from the other channels[citation needed].
[12] In order to maintain the slight downward gradient, the aqueducts didn’t follow a direct route to Rome, but instead used the lay of the land.
The air and water in the cylinders, since the valves close the lower openings, the pistons drive onwards.
[13]Sextus Julius Frontinus wrote a study, De aquaeductu, on the state of the aqueducts of Rome.
Another assertion from Vitruvius is that a structure must exhibit the three qualities of firmitas, utilitas, and vinustas (in English, it must be strong and durable, useful, and beautiful and graceful).
In 1453, Pope Nicholas V renovated the main channels of the Aqua Virgo and added numerous secondary conduits under Campo Marzio[citation needed].
The original terminus, called a mostra, which means "showpiece", was the stately, dignified wall fountain designed by Leon Battista Alberti in Piazza dei Crociferi[citation needed].
