St Lythans

All the stones are mudstone, which, as with those used at Tinkinswood, were probably available locally. The capstone, which slopes downwards from south east to north west measures four metres (13 ft) long, three metres (10 ft) wide, and 0.7 metres (2 ft) thick. The insides of the two facing, rectangular, uprights have been smoothed off and there is a port-hole at the top of the triangular, rear stone (seen in this image) similar to some other dolmens, such as at Trethevy Quoit, in Cornwall.