Dolmen

A dolmen is a type of single-chamber megalithic tomb. It usually consists of three or more upright stones (megaliths) supporting a large flat horizontal capstone (table). 
Most date from the early Neolithic period (4000 BC to 3000 BC). Dolmens were usually covered with earth or smaller stones to form a barrow, though in many cases that covering has weathered away, leaving only the stone "skeleton" of the burial mound intact.