I visited the site on 10th November 2005. To find it, follow the north bank of Afon Disgynfa from the top of Pistyll Rhaeadr to the sheepfolds at SJ061300. Then go about 400 yards up the ridge to the northwest. The circle is on fairly flat ground to the left of the most obvious sheeptrack. Note that it is west of a point on Nant y Cerig-duon before the first side stream forks off. I give this much detail because I initially managed to overshoot the circle without spotting it.
W.F.Grimes (1963) The Stone Circles and Related Monuments of Wales in "Culture and Environment, essays in Honour of Sir Cyril Fox" (eds. I.Foster & L.Alcock) pp.120-122 gives the following description:
"The circle, to the west, has a diameter of about 40 ft. 6 in. It is fairly accurately laid out, but only it's eastern half is well preserved. Here there are 10 stones, of which 9 are in situ; their distances apart vary between 5 and about 10 ft., but the spacing is mostly nearer the lower figure. The stones are mainly a good deal less than 2 ft. high, the tallest being about 30 in. The western half of the circle is almost completely destroyed: here there are only two stones (one of them a small stump) with the hollow for a third, which lies a foot or two away to the south-west. There are other fragments about.
The avenue, lying to the east of the circle, has a present length of 162 ft. It does not actually make contact with the circle, its west end being 14-6 ft. away from the nearest stones of the latter; and there is no reason to believe that it was ever any longer on this side. The width between the stone rows varies between about 8 and about 12 ft.: the rows were no doubt intended to be roughly parallel and there is no progressive increase or decrease in either direction. The present spacing of the stones is very uneven, but it is probable that some are now missing. If there was any uniformity in the distances dividing them, which is by no means certain, a figure of about 5 ft. would be likely. Heights vary between about 4 in. and 18 in. and the stones themselves are often irregular in shape. The north row is less well preserved than the south: it is made up of one stone-hole and 15 stones, of which 5 are down; while on the south there are 24 stones (including 2 pairs) of which 3 are down. The rows are equal in length."
I have posted a copy of the site-plan from Grimes.
The Clwyd-Powys Archaeological Trust on their website record that there are 12 stones visible in the circle, 12 in the northern row and 24 in the southern row.
On my visit I found 16 stones in the circle, 10 in the northern row and 14 in the southern row. I didn't have Grimes's plan with me and I could easily have missed stones in both rows. However it is clear that various stones now visible in the circle are recent additions
We got some directions from the pub owner at the bottom of the waterfall, so we set off on what proved to be the hardest climb we have ever done. We had already walked to the Moel-ty-Uchaf site earlier in the day and thought it would be a perfect way to round off our day. We set off up the mountain, which in a book by A. Burl described as being 'sherpa like' (he was right) we then walked across moors, over bogs and across the stream and found the circle by chance. It was great and I even reset one of the stones which had been knocked over by a sheep.
As we were leaving we caught sight of the stone row which we traced all the way to the cairn, we now know after reading Burls book on stone rows that there was even more to see and that the row was even longer and also on the other side, alas we ran out of time and light. It would be great if the grass etc could be cut down so that people could really see the site. Set in a dramitic setting, away from the world, this site should really be famous.