Penrhos Castle is a ditched motte, about 30m in diameter and 6.0m high, standing towards the south of an irregular oval enclosure, about 40m by 80m, defined by a ditch, with an internal bank on the north-east and having a counterscarp except to the south-east.
It is possibly the castle mentioned as being demolished c.1252.
(source Os495card; SO41SW1)
The castle earthworks appear to be set within the south-west angle of a roughly subrectangular earthwork enclosure, about 160m east-west by 160m, whose eastern side is obscured by a current road; OS County series, 3rd ed. (Monmouth. XIII.4 1920), shows the the scarp of this enclosure's south-west angle where it springs from the south of the castle earthworks.
RCAHMW AP94-CS 0569-70, 1276
RCAHMW AP945075/69-70; 945149/66