Fair enough, this isn't exactly megalithic. But especially for those of a romantic turn of mind this is an important site for those interested in prehistoric Dartmoor.
Dartmoor - like the rest of the country - used to be covered in forest, apart from the topmost tors which were moor as they are today. At the end of the Mesolithic and during the Neolithic, people opened up these forests: first for hunting, then for farming. A combination of the climate and grazing kept the area open and like the Dartmoor we know today.
But in some places, very very few places, there is still oak woodland on Dartmoor. Wistman's Wood is one of these. It clings on to the bottom of the valley side and looks most peculiar as you approach it (it's a walk of a few miles, there's no road). When you arrive you see the wood is made up of tiny twisted oak trees, literally dripping in lichens and mosses. In between the trees is a muddle of boulders, also covered in mosses. You can go in if you like, but we didn't - it's a very important nature reserve and there are some lichens in here that are found in maybe one or two other places in Dartmoor and literally nowhere else. The place is weird and fantastic and like nothing else. I'm not promising it's actually a remnant from the primal forest, but if it isn't it certainly does a good impression. It's been saved from exploitation and grazing by the boulders (originally from the tor above), but such a place is so easily damaged that it's frightening. It makes you feel a bit guilty to be there breathing on it at all but to know such a place exists does your head the world of good.
Wistman's Wood is the place where the Devil (known as Dewer or Old Crockern in these parts) kennels his Wisht hounds. On Midsummer's night he takes them hunting across the moor. Some stories say this is to look for babies who have not been baptised. If you see him and his hounds I'm afraid it's not a very good omen for you. Also, apparently no ordinary dog will ever enter the wood. But I have to say I did see one do this myself. Perhaps it was just foolhardy and never made it out the other side.