Nemi, Lake, a lake in central Italy, about 15 miles (24 km) southeast of Rome. Roughly circular in shape, it has a diameter of almost one mile (1.6 km). It occupies the crater of an extinct volcano. Lake Nemi lies 1,043 feet (318 m) above sea level and has a depth of 112 feet (34 m). On its shores are remains of the sacred woods and temple dedicated in ancient times to Diana. In 1929 and 1930 two large boats of the Roman emperor Caligula were found in the lake, but these were burned by the retreating Germans in 1944. The ancient name of the lake was Nemorensis Lacus.