Dartmoor Walks, a guide that counts them, puts the number of stone circles on Dartmoor at 17, and notes that the generally accepted figure used to be 16. Most are dated to the second millennium BC, within a wider range of about 2500 to 1300 BC given for the circles of the British Isles. That is a broad bracket, and nobody has pinned a date to most individual circles.
The best known pair is Grey Wethers, north of Postbridge: two circles, each about 33 metres across and less than five metres apart, with 20 stones in the northern one and 29 in the southern. Wikipedia records an excavation in 1898 that found charcoal fragments, and a restoration in 1909 that re-erected many fallen stones, so some of what you see was put back by Edwardians. Scorhill, on Gidleigh Common, has 23 stones standing and about 27 metres across, and has not been restored. Fernworthy has 27 smaller stones about 20 metres across, in a clearing in the forest. Merrivale is smaller again, about 19 metres with 11 stones. Brisworthy had only 4 stones standing before its 1909 reconstruction, and Sherberton still has nine of its original stones, with a wall running through the western side.
What were they for? Nobody really knows. The Devonshire Association's Dartmoor Exploration Committee thought they were probably crematoria or sites for funeral feasts. Dartmoor Walks suggests ritual centres and perhaps community meeting places. Both are guesses, and the stones themselves do not say.
One practical note: for Fernworthy, follow the road round Fernworthy Reservoir to its end, where there is a turning area with limited parking, then take the forest road to the clearing on your right.
Bronze Age stone circle and cairn alignment on open moorland south east of Sourton Tors, with later millstone and boundary features.
A Bronze Age ceremonial landscape on Longash Common featuring a stone circle, standing stone, cairn and alignment.
A Bronze Age stone circle on open moorland, where weathered granite blocks mark an ancient gathering place.
A Bronze Age stone circle hidden among Dartmoor's open moorland, its weathered stones still marking an ancient gathering place.
Bronze Age stone circles, cairn and alignment on open moorland.
A Bronze Age stone circle on the open moor south of Little Sherberton.
Two concentric stone circles on Langstone Moor, a Bronze Age monument set among open moorland.
