Did you know? The Nemi Ships were elaborate floating palaces built by Caligula in the 1st Century AD.
Aerial view of the hull of Seconda nave, completely emerged from the waters in 1932
Nothing before on this scale in maritime shipbuilding had been constructed by the Romans, enigmatic and confounding was their discovery, that their purpose to this day is still a subject of speculation. From the size of the ships, it was long held that they were pleasure barges, though, as the lake was sacred, no ship could sail on it under Roman law (Pliny the Younger, Litterae VIII-20) implying a religious exemption.
Discovered in the volcanic lake of Lake Nemi in the Lazio region of Italy, the two vessels had long been known by local fishermen, but were first discovered in 1446 by Cardinal Prospero Colonna and Leon Battista Alberti. The depth of the wrecks at this time made them too deep for salvage (18.3 metres) and attempts at their recovery by Colonna and Alberti only led to significant damage to the preserved timber.
http://www.heritagedaily.com/2016/12/did-you-know-the-nemi-ships-were-massive-elaborate-floating-palaces-built-by-caligula-in-the-1st-century-ad/113593