Apologies if this has been covered elsewhere.
We stopped at Nine Stones the other day (Btw it is now not accessible from the A35 road). I was struck by how uncircular it is. And with its two big stones and seven dwarfs, it is even less of a pure form.
But that is often true isn't it? That don't seem to be that many perfect circles and yet it is such an easy shape to make with a rope and a peg. It is almost as if that wasn't so important - Stonehenge notwithstanding as it is different in so many ways.
So the old description of 'Stone rings' may be better - a space for gathering, an enclosure rather than a circumference.