Avernus

Part of the Phlegraean Fields of volcanoes,[1] Avernus is approximately 3.2 kilometres (2.0 mi) in circumference.

On the shores of the lake is the grotto of the Cumaean Sibyl and the entrance to a long tunnel (Grotta di Cocceio, c. 800 metres (2,600 ft)) leading toward Cumae, where her sanctuary was located.

During the civil war between Octavian and Antony, Agrippa tried to turn the lake into a military port, the Portus Julius.

[6][7] The term avernus (plural averni) was also used by ancient naturalists for certain lakes, grottos, and other places which infect the air with poisonous steams or vapors.

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