Pentwyn defended enclosure is located on a narrow neck of rough pasture moorland on the south-eastern margins of the Black Mountains. It consists of two conjoining enclosures flanked by farmland on the south-west and steep natural slopes to the north-east. A subrectangular enclosure measuring about 140m by 70m, defined by a bank and ditch has a south-east entrance that opens into a sub-oval area measuring about 185m by 104m. The defences are multivallate aside from the more naturally defended north-east side.
Sources:
OS record card SO32SW6.
RCAHMW air photos: 945074/42-3.

D.Leighton & J.Wiles, RCAHMW, 7 April 2016