Now that they have been swallowed by landslides and vegetation, the supporting structures of the once-spectacular Via Flacca are nearly unnoticeable. This ancient Roman road was built by the censor Lucius Valerius Flaccus in the second century B.C. As the nearby Villa of Tiberius shows, the coastline was a popular site for the wealthy to build their seaside villas. The road also provided an alternative route to pass the rugged coastline and the Aurunci mountains, connecting Sperlonga to the ancient Via Appia.

The road was an elaborate, complicated, and perilous project, which was only replaced by the present road in the late 1950s. (The modern paved road is named after the old Via Flacca.) Not much is left of the ancient road, but a few short segments can be accessed on an abandoned trail network that connects Sperlonga with Sant'Agostino beach, at heights ranging from 15 to 60 meters (50-200 feet) above the sea below.

The most interesting remains, consisting mostly of large squared or polygonal rocks set against the cliffs, are visible on the first headland, Punta Cetarola, and can be accessed from a trail which runs on the side of the first tunnel. The trail itself follows the old Via Flacca and enters a spectacular natural cave, known as the Antro di Punta Cetarola, which is open on either side. Before and after the cave the trail is entirely built on the top of the old Roman supporting stones.

After this short stretch, the trail might be impassable due to the thick vegetation or frequent landslides. It might be safer to walk through the tunnel. A second headland, further north, also preserves a short stretch of the old trail which leads to a 16th century lookout tower, Torre Capovento, a reminder of the times in which Saracen pirates and corsairs terrorized the coast. The tower was also used as a customs house in later times. It is mostly in ruins, but provides a beautiful view on the cliffs of the Riviera di Ulisse marine reserve, and the stunning medieval town of Sperlonga.

Once more, the trail becomes impassable after the tower and one needs to backtrack to the tunnel. At the end of the following beach, the trail is well preserved, it rounds the headland above the Villa of Tiberius and descends to the archaeological site. A pedestrian path then leads from the Villa to the town of Sperlonga, recognisable by its white houses and the Truglia tower reaching out over the sea.