The Lago d'Averno, just a few kilometers west of Naples, is a quiet crater lake surrounded by vineyards and laurel trees. In antiquity, it was considered a mythical place – poets such as Virgil described it as the entrance to the underworld. On the northeastern shore of the lake stands an impressive ruin from the Roman Imperial period, long referred to as the "Temple of Diana" or "Temple of Apollo." In reality, it is the remains of a monumental thermal hall – a fascinating example of Roman architecture and part of a largely forgotten cultural landscape.
A "Temple" at the Lago d'Averno That Never Was
As far back as the 18th and 19th centuries, travelers gave the ruin various names: at times it was the temple of the moon goddess Diana, at other times a sanctuary of Apollo, fitting the region's Sibylline tradition of prophecy. Archaeologically, however, no direct connection to a temple cult can be established.
The structure, a large domed brick building with an apse, niches, and water channels, suggests rather that it was part of an ancient thermal or nymphaeum complex. The building most likely dates to the 1st or 2nd century AD and stands as a prime example of the technical mastery of Roman engineers in their use of concrete, vaulted construction, and hydraulic engineering.
A Location at the Cultural Heart of Antiquity
The Lago d'Averno was by no means a remote location in Roman times. It lay at the center of the Campi Flegrei – a densely populated area filled with villas, thermal baths, and sanctuaries. In close proximity were Cumae with its famous Temple of the Sibyl, the seaside resort of Baiae, and the harbor of Portus Julius. The hall at Lake Averno may have been part of a larger bathing complex or recreation center, possibly even serving spiritual functions.
Its strategic position on the lakeshore points to a deliberate sense of staging: water, architecture, and landscape interlocked here in a remarkably compelling way. In this sense, the hall can certainly be understood as a site of representation and the cultivation of the Roman way of life.
Today: A Walk Between History and Nature
The ruin is publicly accessible today and sits directly along the well-maintained circular path around the Lago d'Averno. The footpath winds through dense vegetation, past grapevines, ancient stone walls, and sulfurous vaporsrising from the ground. The lake is calm, almost mystical, and visited by few tourists, making it ideal for those who appreciate historic sites in a natural setting. It also serves as a recreational area for the local community.
There are no admission fees, no signage, and no barriers, allowing for a spontaneous and unhurried visit. The ruin itself is well preserved and particularly rewarding to photograph, especially in the morning or evening light.