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The Nemi ships were two ships, one larger than the other, built under the reign of the Roman emperor Caligula in the 1st century AD at Lake Nemi.
Local fishermen had always been aware of the existence of the wrecks, and had explored them and removed small artefacts, often using grappling hooks to pull up pieces, which they sold to tourists.
De Marchi apparently sold everything he collected to the nobility and foreign visitors who visited the site to watch his work.
From material recovered he added the knowledge that mortise and tenon joints had been used in their construction.
Recovered from the lake bed in 1929, the ships were destroyed by fire during World War II in 1944.
(0.64 sq mi) and a maximum depth of 33 metres (108 ft).