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.
More generally, any megalithic tomb, including passage graves and wedge tombs.
A prehistoric enclosure in the form of a circle or circular arc defined by a raised circular bank and a circular ditch usually running inside the bank, with one or more entrances leading into the enclosed open space.