What is the X in X-mas?
prehistoric grave found in the Balearic Isles. The naus was built of closely fitting blocks of stone in the shape of an overturned boat with a rounded stern and a squared or slightly concave front. A small door in the front gave access to a slab-roofed passage leading to a long, rectangular burial chamber. Constructed during the Bronze Age, the graves were the equivalent of the long barrow, or cairn, of western Europe.