added by archaeologs A series of stones set up in a ring, the commonest prehistoric monuments of England, such as those at Avebury and Stonehenge. Most were of stone, though some were of wood or a combination of the two. They vary greatly in size, from a few feet in diameter, to those which are a 1/4-mile in diameter and huge monoliths of 60 tons. Some circles have monoliths in the center and some smaller circles have burials in the center.