Grotta di Seiano

In Posillipo, where Naples looks towards the sea and the Phlegraean Fields, the Grotta di Seiano is one of the city’s most surprising passages. It is not a natural cave, but a monumental tunnel carved into the tuff rock, connecting the Bagnoli plain with the Gaiola valley and the archaeological area of Pausilypon.

Walking through it means entering both the rock and the history of Naples: an underground route that opens onto one of the most fascinating landscapes of the Gulf, between Roman archaeology, Mediterranean nature and sudden views of the sea.

A Roman engineering work

The Grotta di Seiano is a Roman tunnel over 700 metres long, created to connect the Bagnoli area with the Gaiola side of Posillipo. According to the Gaiola Marine Protected Area, the complex accessed through the tunnel includes remains of the ancient villa of Pausilypon, built in the 1st century BC by the Roman knight Publius Vedius Pollio.
The tunnel takes its name from Lucius Aelius Sejanus, prefect of Emperor Tiberius, traditionally associated with later works of enlargement and improvement. Its purpose was both practical and strategic: to connect the aristocratic villas of Posillipo with the ports and routes of the Phlegraean area.

From underground Naples to the landscape

The experience of the Grotta di Seiano is based on contrast. Visitors enter a long, silent tuff tunnel and then emerge into an open, luminous space overlooking the sea and the coast.

The Municipality of Naples describes the area as being of great naturalistic, archaeological and landscape interest, adjacent to the Gaiola Marine Protected Area and extending from the Trentaremi promontory to the Gaiola valley.

The entrance to the Archaeological Park of Pausilypon

The Grotta di Seiano is the main access to the Archaeological and Environmental Park of Pausilypon. After crossing the tunnel, the route leads to the theatre area and to the remains of the great Roman villa built in the 1st century BC by Publius Vedius Pollio, as also recalled by the Italian Ministry of Culture.

The name Pausilypon comes from Greek and is traditionally interpreted as “the place where pain ceases”. Even today, this definition seems to describe the atmosphere of this stretch of coast, where landscape, silence and ancient memory shape the visit.

A key stop towards the Phlegraean Fields

Within the itinerary “Towards the Phlegraean Fields”, the Grotta di Seiano is a key stop. It marks the moment when the route leaves the urban dimension and opens onto a more geological, archaeological and coastal Naples.

From here, visitors can better understand the connection between Posillipo, Bagnoli, Gaiola and the Phlegraean area: a system of places where tuff rock, sea, Roman villas and panoramic views tell a different story of the city.