Carreg Waun Llech is a large weathered limestone block standing 387m above OD in a marshy hollow on a limestone plateau in open moorland. It is 2.62m high, a maximum of 1.27m broad (tapering towards the top) and 0.4m thick. Features resembling cupmarks appear on the east and west faces but these are almost certainly due to natural erosion. It leans about 10 deg. to the east but has a general orientation north-east by south-west.
This stone has probably been a boundary marker between Llangatwg and Llangynidr since medieval times, marking an angle in the parish boundary.
Source:
RCAHMW, Brecknock Inventory vol.1 pt.1 (1997), p.174 (SS27).
