Lago d'Averno

A quiet crater lake a short distance from the Tyrrhenian shore, Averno belongs to the closing chapters of Phlegraean volcanism and to the oldest pages of Latin poetry: Virgil placed the gate of the underworld here, reached by Aeneas after consulting the Sibyl at nearby Cumae.

Why it matters

No Italian lake carries a heavier load of myth. To the ancient world this round sheet of water was the very entrance to the realm of the dead — Virgil calls it the gate of Dis in the sixth book of the Aeneid — and the reputation was old long before the poem: Strabo already recorded the legend that birds flying over the water fell dead, which gave the lake its Greek name Aornos, "birdless". The place was served by priests, held an oracle, and even had its own god, deus Avernus. Science has since rewritten the scene — Treccani notes that the famous poisonous exhalations left no trace, and that coots were observed living unharmed on the water centuries ago — but the geology behind the story is real: the lake fills a crater of the Campi Flegrei volcanic field, where the Instituto Nazionale di Geofisica e Vulcanologia places the most recent epoch of eruptive activity between about 5,500 and 3,800 years ago, and where the 1538 birth of Monte Nuovo, right beside the lake, remains the volcano's last eruption. Myth, poetry and live volcanism occupy the same shoreline.

What to notice

The lake has an oval perimeter of roughly 2.9 kilometres, a surface area of 0.55 square kilometres, a maximum depth of thirty-four metres and an elevation of about two metres above sea level. Green crater walls rise around its shore. On the eastern side are the ruins traditionally called the Temple of Apollo, a Roman bath building with a large octagonal hall. Toward ancient Cumae, the hill conceals the Cumae entrance of the Grotta di Cocceio, the tunnel Agrippa's engineers drove through the rock. The lake was once salt water connected to the sea and later became a freshwater basin.

Context and history

Ancient writers disagreed about the lake's darkness only in detail. Strabo described banks once wrapped in a dense sacred grove; the priests who administered the site required sacrifice before entry; a nearby spring was shunned as Stygian water, while hot springs close by were read as the fire-river Pyriphlegethon of the underworld geography. Virgil made the association permanent: in the Aeneid, Aeneas consults the Sibyl at Cumae and passes from there towards Averno's gate of the underworld, and the park's narrative credits those verses with drawing visitors and scholars to the site ever since. History then militarised the myth: between 44 and 31 BC Agrippa, working for Octavian, built the Portus Iulius, the naval complex that joined the lakes and the sea into a hidden fleet base against Sextus Pompey — Treccani's entry on Cumae names Averno, with Cumae and Miseno, as the core of that formidable naval base — and Cocceius' tunnel tied the lake to the city. The volcano itself stayed in the picture: the caldera's third post-caldera epoch ended around 3,800 years ago, and in 1538 Monte Nuovo rose in a week of eruptions, the field's last. Bradyseism has partially buried the bath ruins, as noted in the park's account of the lakeshore.