I approached via Moretonhampstead but in the jumble of roads and junctions in the middle of the small town I couldn't honestly give good directions to find the lane that leads up to the downs! I can say that it isn't signposted at all and it might have been 'School Lane'(?). I just felt the lane was the right one judging from the OS map. If you then go down and back up a dip, and pass Addiscott on your right you are on the right lane! I left the downs due south, onto the B3212 (which by the way is a really twisty and narrow B road for much of its length), which was really easy so this might be a better way.
This is all Access Land, so you can roam at will. There is a sort of 'car park' at SX762873. If you are coming onto the common from the south west, take the road to the right (marked 'Exeter') and it's 200m up the road on the left. However, all it is is the only tarmaced area on the common. No facilities. In fact when I was there most of it was taken up with mounds of gravel. In reality people park all over the downs as most of the roads have clear spaces off of them at intervals (and they aren't passing places).
There are loads of paths all over the downs. All seem pretty basic and liable to mud. Some might get overgrown in summer. Gorse almost everywhere. The car park is a relatively convenient place to park as there is a clear path up to the top. However this is a bit more of a climb (55m in height in a 500m walk) than from the south end.
The track that is marked on the OS map that goes across the top of the hill doesn't really live up to it's billing and exists only in places as a track wide enough for a 4x4. Some of the time it's just like a footpath, and can be boggy. But it is a convenient way to help find the ancient sties on this hill.
At 356 metres above sea level there are not surprisingly brilliant views from the hill.
There are plenty of parking places, three that I can see on Google earth, I parked on the west side and followed the obvious and worn path straight to the top. Passing the flattened ring cairn to the junction of paths, right takes us to the stone circle, the biggest on Dartmoor. Left takes us past the often disappointing Giants grave and friend. Keep going, past confusing mortar pits until you get to the cairn circle. Bosh, done.
Apparently this site confuses some people, is it a small stone circle? a cairn with a stone circle or even a hut circle? an enlightened chap called Jeremy Butler said this "it is unparalleled among the numerous cairns on the moorland massif only a short distance to the west, emphasizing the very localised nature of some cairn designs". The confusion arises I think because of peoples need to pigeon hole all monuments, everything has to be of a type, it's all got to be named, give it a name and we can add it to the list of known things.
Mardon down doesn't care about your wants or needs, it is what it is, but, what is it?
It's a wondrous thing, that's what.
Big stones in a small space.
Looking north away from Dartmoor the views are long, sit around and wait for the sun to come back out and the whole scene is just brilliant.
In the end, I think it's a cairn with some very pronounced circle stones, it reminded me of the very distant Bryn Cader Faner.
There are loads of cairns up here, some are more cairnish than others, the ring cairn type one the big stoned kerb cairn, the grassy bump type and the stone rubble with a pit in type. But, the latter is not a cairn, there is one on the circumference of the stone circle, that's not a cairn, there is one by the Giants grave, that's not a cairn either. They are both in fact mortar pits dug by practicing soldiers waiting for D day in WW2. Perhaps a more poignant type of monument than most cairns, or perhaps not.