Interesting...I can see it on the photo although I don't remember it being particularly striking from the couple of times I've been there.
One has to be careful as there are a lot of natural boulders lying around (as one of the other pics shows i think) but, as the stones of 275 itself are pretty low anyway, it could be.
Does anyone know if this has got a better name, or indeed why it's called 'Circle 275'?