The remains of the ancient town can be visited
Porta San Sebastiano

The Porta San Sebastiano, once known as Porta Appia, is an ancient city gate that forms part of the Aurelian Walls in Rome. It marks the beginning of the Via Appia Antica outside the city walls.
History+
Originally equipped with two arches and semicircular towers, the gate underwent several modifications. Between 401 and 402 AD, Emperor Honorius had the towers and the central section raised and reinforced by one story. The Porta San Sebastiano was secured with gate wings and a portcullis. In 536, after the conquest of Rome, the Eastern Roman general Belisarius further expanded the gate using existing marble blocks and added the robust semicircular side towers still visible today.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://en.wikipedia.org/wiki/File:Porta_St._Sebastiano_Rome_2011_1.jpg
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 41.8735, 12.5015