Avernus

Circular lake in Campania, southern Italy, 4 km/2.5 mi northwest of Pozzuoli. Lying in the crater of an extinct volcano, it is 2 km/1 mi in circumference and 65 m/213 ft deep. The Romans, including the poet Virgil, believed it to be the entrance to the lower world because it formerly gave off fumes which killed birds.

Remains of Roman baths, including a lofty octagonal hall called the Temple of Apollo, are on the eastern shore of the lake. During the Roman Empire Avernus became a naval base linked by canal to Lake Lucrino, and from there to the sea. Cocceio's Cave, an underground passage (1 km/0.5 mi long), connected the lake with the ancient city of Cumae, and was used by chariots.