Small hillfort separated from the Mynydd Llangatwg scarp by the Nant Onneu. Coflein (J. Wiles, 2002) has this:
The defended enclosure at Coes Pentwyn is an irregular defended site occupying a ridge terminal. Bivallate defences define the west of a roughly heart-shaped enclosure measuring c138m by 75m, and completed by scarps elsewhere. There is an involved inturned entrance on the north.