Lake Nemi, Volcanic crater lake in Alban Hills, Italy

Lake Nemi is a small circular volcanic crater lake in the Alban Hills, about 30 km south of Rome, formed in a crater at least 36,000 years old. Its deep blue water fills the basin, enclosed by a tree-covered slope that rises to a ridge where the town of Nemi stands. The lake has no natural outlet; its level was controlled in antiquity by an emissary tunnel 1,650 m long cut through the crater wall to Vallericcia.

The lake served as a sacred site in ancient times and maintained its religious importance throughout the Roman period. In the 20th century, the receding water level exposed the remains of two ancient imperial-era vessels that had rested on the bottom for nearly two thousand years.

The name Nemi comes from the Latin Nemus Dianae, the sacred grove of Diana, whose temple stood by the shore before the falling water level left it further inland. The Nemoralia festival was held here from the 6th century BC, and a priest called the Rex Nemorensis reigned in the grove until a challenger killed him, a practice recorded in Frazer's The Golden Bough.

Shore access varies because much of the lake is surrounded by private land, so check local conditions before planning a visit. The area is easily reached by car, and parking is available near the main viewpoints around the water.

The two ships, 70 m long and over 25 m wide, were raised between October 1928 and October 1932 by lowering the lake with pumps; the level never returned to its original height. In the night of 31 May to 1 June 1944 a fire, probably arson, destroyed them in the museum.