Pen y Gaer is an oval defended enclosure circa 174 metres by 80 metres that is sited on a knoll on the north-east to south-west ridge. There is an irregular internal topography, defined by scarps, except to the south-west, where there are remains of a bank and a ditch. The site was visited by the RCAHMW on 4 November 1909 and by Clwyd-Powys Archaeological Trust in 1978 and 1991.

Claire Parry, RCAHMW, 10 August 2011.

Source:
Inventory of the Ancient Monuments in Wales and Monmouth I - County of Montgomery , Royal Commission on the Ancient and Historical Monuments of Wales , 1911
Clwyd-Powys Archaeological Trust Historic Environment Record