Iron Age hillfort occupying a steep sided, isolated knoll separated from a longer ridge 'Parc yr Hydd' on the north side by a natural ravine and by steep slopes to the valley floor of the Nant Faen on all other sides. The 'Castell' place name provided an indication of an antiquity hereabouts, but the existence of the hilltop enclosure was only documented by J. Bezant, Trinity St. Davids University, in 2013. Subsequently the enclosure was noted on Digital Terrain Model data derived from Environment Agency LiDAR.

The LiDAR model of the hillfort shows an elongated oval enclosure c.111m east-west by 34m north-south, defined by precipitous natural slopes on the north and west sides, but by a well-defined rampart on the south and east sides. Some mounds and structures are visible within the enclosure. J. Bezant describes the rampart as a dry-stone revetted bank. She notes there is some evidence of an internal ditch across one end, and that the site seems similar in scale to two other nearby sites at Y Gaer (NPRN 303835) and Bronfe Ganol (DAT HER 11831). She also notes that the specific geology perhaps lends itself to this site type here - 'Ciliau'.

T. Driver, RCAHMW