Dyffryn Mymbyr

Answers are less forthcoming...

Whatever it is, it's definitely man-made, but the question of "when?" is obviously much less easy to answer. It's not a circle, but an ellipse - the diameter E-W is a couple of yards more than the diameter N-S. The stones are all slender (apart from the off-centre stone within the circle, which appears natural) and have obviously been selected for the purpose of putting up on end. They are comparable size-wise with the bigger stones at Cerrig Pryfaid, about 10 miles distant as the crow flies. They are not the kind of stones you would use in the footings of a hut circle or sheep pen, as they're too thin. There's a degree of "wobble", but not unexpected given how waterlogged the site is. The setting is stunning, in a natural amphitheatre below the Glyderau with views of Crib Goch/Y Lliwedd across the pass.

The top of a smaller stone, very earthfast, protrudes on the southern arc of the circle (see Gladman's pics) and I suspect that there are probably more smaller stones hidden under the water, mud and vegetation.

I'd like to think it could be a prehistoric circle, but unless someone drains the site and removes the top layers it seems unlikely we'll know for sure - perhaps a drought might expose more, as has happened at various Dartmoor sites of small stones. A few walkers with nothing better to do could have put it up, but there is drier land within 100 yards that would have been a more attractive proposition for a folly of that sort, and I don't think it seems likely. But if it isn't it a prehistoric circle it has no obvious other purpose or function that I can think of.

We had a great day, thanks. Wellies were definitely appreciated - even the simple walk from Pen y Gwyrd was a waterlogged nightmare.

Yep, it was - the tops were in heavy cloud but we were nice and sunny.

Glad you went back, hopefully fully equipped.