The cairn, located about 270m SSE of the summit of the mountain, is a stony mound 6.1m in diameter and 0.6m high. At centre is a hollow deep from which a cist has been removed. Four slabs, each lie on the surface. Many neolithic arrowheads have been found at the site, and there is a belief that an ancient faerie battle happened here. Wirt Sikes British Goblins tells the tale:
There is a tradition among the Glamorgan peasantry of a fairy battle fought on the mountain between Merthyr and Aberdare, in which the pygmy combatants were on horseback. There appeared to be two armies, one of which was mounted on milk-white steeds, and the other on horses of jet-black. They rode at each other with the utmost fury, and their swords could be seen flashing in the air like so many penknife blades. The army on the white horses won the day, and drove the black-mounted force from the field. The whole scene then disappeared in a light mist.