Dinas Powys Castle is a ruinous medieval fortress crowning a small and isolated steep-sided hill. It was the centre for a wealthy lordship. The castle is first recorded in about 1200 and was 'al in ruine' by the early sixteenth century. Thirteenth to fifteenth century coins have been found at the site.

The castle consists of a near rectangular walled court about 68m north-west to south-east by 32m. The wall is 2.0m wide and in places survives to its battlements. There was a wide arched entrance facing the main approach from the south-east and a narrower postern with a pointed arch in the north-east wall. Masonry and timber buildings, including a great lordly hall, once lined the walls. At the north-west end there are slight remains of a great rectangular tower, some 18m by 13m, attached to the outside of the enclosure wall. A small counterscarped outwork, apparently earlier than the enclosure, lies beyond the tower.
It is thought that the tower is earlier than the enclosure and it was probably built in the twelfth century. The enclosure may be late twelfth century, although the form of the postern hints at a thirteenth century date.

Source: RCAHMW Glamorgan Inventory III.1a The Earlier Castles (1991), 307-314

John Wiles, RCAHMW, 14 February 2008