A ruinous Bronze Age round cairn, 15m in diameter & 0.4m high, is set on the summit of Pen y Garn. Only the base of the cairn has survived, the rest of it used to create a shelter which now occupies most of its interior. Towards its north edge, between shelter and cairn edge, is set a triangulation pilar.

D. Leighton & T. Driver, RCAHMW, 17 June 2013