Naveta Es Tudons

A naveta is a megalithic chamber tomb unique to the Balearic island of Minorca. It dates to the early Bronze Age. It has two vertical and two corbelled walls giving it the form of an unpturned boat which is where the name comes from.

The largest example is the Naveta des Tudons which is around 4m high, 14m long and 6.4m wide.

http://en.wikipedia.org/wiki/Naveta