dolmen

noun2

1. •
   Any megalithic tomb, including passage graves and wedge tombs.
2. •
   A prehistoric megalithic tomb consisting of a capstone supported by two or more upright stones, most having originally been covered with earth or smaller stones to form a barrow.

   • They are expert smiths and coiners; they are said to have great treasures in the dolmen in which they dwell, and of which they are regarded as the builders. — 1850