The rectangular enclosure at Bwlch Blaen-Corn measures 80m x 50m, has a good inner bank and outer ditch, and is sited on a narrow plateau between steep cliffs on SE side and rising ground on NW side. The Roman road, Sarn Helen, to Careg y Bwci passes within 30m on W side, and this enclosure is slighted both by present road and by earth field banks which cross parts of it. The site was discovered during RCAHMW aerial reconnaissance on 31 Jan 2003.
Subsequent fieldwork in 2007/8 by Ken Murphy (DAT) and Dr Jeffrey Davies in advance of a new 'Roman Frontiers of Wales' publication identified it as a Roman fortlet.
