The remains of the ancient Servian Wall can be visited
Mura serviane (Servian Wall)

The Servian Wall in Rome is one of the oldest city walls. It shaped Rome's security.
History+
The origins of the Servian Wall are traditionally attributed to the Roman king Servius Tullius, who reigned from 578 to 534 BC. Under his successor Tarquinius Superbus, the wall is said to have been further reinforced and especially heightened in the area of the Agger Tarquinii. However, the remains visible today date from the 4th century BC. After the Celtic conquest of Rome following the Battle of the Allia, the censors commissioned the reconstruction of the wall in 378 BC.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://de.wikipedia.org/wiki/Datei:Servian_Wall-Termini_Station.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: 41.9019, 12.5017