Lake Avernus — Gateway to the UnderworldRoman Mythology

In Book VI of Virgil's Aeneid, the Trojan hero Aeneas — guided by the Sibyl of Cumae — descends to the underworld through a cave near Lake Avernus. The lake's dark waters, its sulfurous vapors, and the fact that (according to ancient accounts) no birds flew over it made it the obvious portal to the realm of the dead.

Aeneas crosses the river Styx with the ferryman Charon, passes the three-headed dog Cerberus, traverses the Fields of Mourning and the Fields of the Blessed, and finally reaches his father Anchises in Elysium. There, Anchises shows him a parade of future Roman souls waiting to be born — a prophecy of Rome's destiny culminating in Augustus himself. The passage is the foundation of Western literary depictions of the afterlife, influencing Dante's Inferno 1,300 years later.

The Greeks had already associated the area with death: the Oracle of the Dead (Necromanteion) at nearby Cumae was one of the most famous in the ancient world. The volcanic landscape of the Phlegraean Fields — bubbling sulfur, steaming vents, shifting ground — made the connection to the underworld viscerally real.

Lake Avernus is a volcanic crater lake in the Campi Flegrei (Phlegraean Fields), a supervolcanic caldera west of Naples. The nearly circular lake is about half a mile across and 200 feet deep, surrounded by steep, wooded slopes. The name may derive from the Greek aornos ('without birds'), though plenty of birds are visible today.

The Phlegraean Fields remain volcanically active — the ground around Pozzuoli has risen over 6 feet since the 1980s due to underground magma movement. The nearby Solfatara crater, with its hissing fumaroles and sulfurous mud, vividly demonstrates why the ancients associated this landscape with the underworld. The Cave of the Sibyl at nearby Cumae — a dramatic trapezoidal tunnel cut through rock — is also visitable.

Virgil wrote the Aeneid between 29 and 19 BCE, drawing on much older Greek traditions associating the Phlegraean Fields with the underworld. The Greeks established the colony of Cumae nearby in the 8th century BCE, and the Oracle of the Sibyl was already ancient in Virgil's time.

Agrippa transformed Lake Avernus into a military harbor (Portus Julius) in 37 BCE by cutting a canal to the sea, but the harbor silted up within decades. Archaeological remains of Agrippa's tunnel and Roman bath complexes ring the lake. Robert Temple's investigation of the 'Great Antrum' — a system of tunnels near the lake — suggests it may have been used for ritual descent experiences mimicking a journey to the underworld, with heated sulfurous water creating the sensory impression of crossing the Styx.