This dolmen structure is what St. Lythans would have looked like if it was more complete - but this one is bigger. It would have been completely covered in soil like a barrow mound - but the structure is different and so they call them dolmens instead. The large stone on top is a record breaking size - it is considered the largest dolmen capstone in Europe.
Legend has it that anyone who spends a night at Tinkinswood on the evenings before Beltane, Midsummer or Samhain - or the Three Spirit Nights, would either die, go mad, or become a poet.
In Wirt Sikes British Goblins there is an interesting associated with this place and what they call the Fairies in Brittany:
There is a remarkable cromlech near the hamlet of St Nicholas, Glamorganshire, on the estate of the family whose house has the honour of being haunted by the ghost of an admiral. This cromlech is called, by children in that neighbourhood, 'Castle Correg'. A Cardiff gentleman who asked some children who were playing round the cromlech, what they termed it, was struck by the name, which recalled to him the Breton fairies thus designated. The korreds and korregs of Brittany closely resemble the Welsh fairies in numberless details. The korreds are supposed to live in the cromlechs, of which they are believed to have been the builders. They dance around them at night, and woe betide the unhappy peasant who joins them in their roundels.