The large hillfort at Mynudd-y-Gaer crowns the summit of an isolated hill, the mountain of the fortress. The fort is roughly 220m east-west by 180m and was originally enclosed by a stony rampart or wall, with a ditch and outer bank or counterscarp. The track of the ramparts is roughly hexagonal. On the north side there is a staggered entrance where the ramparts overlap. On the eastern side, where the fort faces generally level ground, the ramparts are doubled with an inner stretch of rampart, ditch and counterscarp. There is a second possible entrance on this side.
Hillforts are characteristic of the later-Prehistoric period or Iron Age, although many appear to have been maintained and some established anew, across the Roman period. The polygonal plan of Mynydd-y-Gaer is unusual, as is the staggered form of the entrance. It is possible that this is a relatively late foundation, perhaps early medieval, and it is even possible that it is a rather later encampment.
Source: Davies 'The Prehistoric and Roman Remains of Denbighshire' (1929), 291-3
John Wiles 27.07.07