This stone can be found not far from Maen Llia. It is a 3 dimensional representation of the same triangle that defines the layout of Maen Llia, the Henge and Rhyd Uchaf cairn.
Image credit: cerrig
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I know coincidences do abound, but one really does wonder what might have been going on up here.........
I wish I knew, Gladman. It seems that every new find poses more questions. This stone is part of a whole monument in its own right, which confirms much that has already turned up with Maen Llia, and links it to other prominent sites too.
Pm me on MegP and I'll tell you where it is, if you can keep it quiet for a little while, official authentication pending.