Porta Prenestina
Coordinates: 41°53′29″N 12°30′55″E / 41.891512°N 12.515144°E
The Porta Maggiore ("Larger Gate"), or Porta Prenestina, is one of the eastern gates in the ancient but well-preserved 3rd-century Aurelian Walls of Rome.
Through the gate ran two ancient roads: the Via Praenestina and the Via Labicana. The Via Prenestina was the eastern road to the ancient town of Praeneste (modern Palestrina). The Via Labicana (now called the Via Casilina) heads southeast from the city.
The Porta Maggiore is by far the best urban site to visit for an understanding and view of the ancient aqueducts. It is a monumental double archway built of white travertine. It was first known as the Porta Prenestina, perhaps a reference to the road over which is passes (the Via Praenestina). The "gate," built in 52 AD by the emperor Claudius, was originally intended to provide a decorative section of support for two aqueducts, the Aqua Claudia and the Anio Novus. At that time these aqueducts crossed the ancient Via Labicana and Praenestina roads thereby providing the opportunity to create at this location a sort of triumphal arch to the conquest of nature and its conqueror, the emperor Claudius. The two channels of these aqueducts, (the Aqua Claudia and Aqua Anio Novus), one lying on top of the other, can be seen when viewing the cross-section running through the travertine attic at the top of the gate.
The gate was incorporated in the Aurelian Wall in 271 by the emperor Aurelian thus truly turning it into an entrance (gate) to the city. Experts refer to this as an early example of “architectural recycling,” essentially adapting one existing structure, to another use. In this case using an aqueduct as a wall.
...
Wikipedia