The Grotta di Cocceio is an ancient Roman tunnel nearly a kilometre in length connecting Lake Avernus with Cumae and dating from 38-36 BC. It was burrowed through the tuff stone of Monte Grillo by the architect Lucius Cocceius Auctus at the command of Agrippa who was in the process of converting the Lake into a military port, the Portus Julius.
Description via Wikipedia. Coordinates and heritage data from the Atika atlas.
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