1. Ordnance Survey description: Three large ramparts and ditches rise one above the other to form a very impressive defence on the NE side of this promontory enclosure, which otherwise rests on the crags and scarps of Corn y fan. There is an entrance to the NE, between the ramparts and the crags, and a quarry ditch within the innermost rampart. The interior, c.48m by 8.0-16m and innocent of traces of occupation, seems small in relation to the scale and extent of the defences. The site is significant for its visually dominant position.
(Source: OS 495 card; SN93NE1)
2. Royal Commission Brecknock Inventory (1986), 41-3:
The fort consists of a triple system of banks and ditches defending the summit of a prominent knoll which stands 350 m above O.D., 2 km S. of Merthyr Cynog. The area enclosed is small and irregularly oval in shape, measuring about 50 m N.E. to S.W. by between 16 m and 20 m, an area of 0.09 ha. The S. edge of the site is formed by sheer cliffs, and elsewhere the ground slopes down steeply from the summit. The site would have been very difficult to approach except from the N. and N.E. against which the defences are set. The fort has commanding views of the middle reaches of the Afon Ysgir valley.
The earthworks are well preserved for the most part. Ploughing has obscured the outermost ditch which is only faintly discernible, and quarrying of uncertain date has destroyed some details of the entrance approach on the E. There are three, close-set, curving ramparts of earth and stone, now grass- and treecovered. The spacing between the centres of the bank crests averages just over 10 m between the inner and middle and just under 10 m between middle and outer. The broadest spacing, over 11 m, occurs at the E., entrance, end. All three banks are inturned at their W. ends, the inner particularly sharply. The E. end of the outer bank is inturned also. The maximum surviving heights of the inner and outer scarps of the banks, taken in succession outwards, are respectively 0.2 m, 4.2 m, 0.3 m, 3 m, 0.3 m and 3.9 m. The ramparts were probably built according to the technique termed downward construction,' whereby the material for the rampart was heaped downwards on the hillslope from a quarry ditch above, and the process repeated for the other two banks by excavating the inner and middle ditches. The outer ditch may have been relatively shallow, providing some upcast for the outer bank and possibly some for a low counterscarp bank which, if it existed, is no longer visible. An irregular ditch up to 1.2 m deep can be traced behind the inner rampart. There is no convincing evidence of a suggested fourth, more widely spaced, rampart on the W.
The entrance approach is from the N.E. up a Vshaped stretch of sloping ground between the ends of the earthworks and the sheer slopes and crags of the S.E. side. In its present form this approach seems more poorly defended than is consistent with the strength of the main defence. It is possible that the change of slope at the edge of the most easterly of the more recent quarries in this area is the severely damaged remains of some additional protection and that other works have been destroyed. A narrow passage is formed between the end of the main inner rampart and a short length of bank along the cliff edge, and here there was probably a gate.
The surface of the interior is very irregular, the main features being two rock bosses separated by a hollow. The least exposed and most habitable area is the base of the quarry ditch behind the inner rampart.
Updated by Dr Toby Driver, RCAHMW, March 2025
Reference:
RCAHMW 1986. An Inventory of the Ancient Monuments in Brecknock (Brycheiniog). The Prehistoric and Roman Monuments. Part ii: Hill-forts ad Roman Remains. HMSO.