Grotta di Cocceio, also known as the Cocceius Tunnel, is a straight-line subterranean gallery nearly a kilometer in length connecting Lake Avernus with Cumae north of Naples, Italy. It was burrowed clean through the tufa stone of Monte Grillo from 38-36 BCE. The tunnel was effected by the architect Lucius Cocceius Auctus at the wishes of Agrippa who was in the process of converting the Lake into a military port, the Portus Julius . The Avernus side of the passage was decorated with a colonnade and had many statues in niches hewn into the tufa stone walls of the entance.
It is also known as the Grotta della Pace in reference to a Spanish captain, Pietro de Pace, who made use of the tunnel in 1508-1509 to plunder the ruins of Cumae as yet still bearing rich items.
The Grotta was heavily damaged during World War II and is no longer open to the public.
