The Cwm Berwyn Defended Enclosure is defined by a bank and ditch that cut off the northern and western approaches to an irregular area approximately 70m by 88m. It is otherwise defined by crags and steep scarps. A second line of bank and ditch, approximately 20m northward, has a frontage of about 92m. It is set on the butt end of a south-east facing spur.

The inner rampart is 1.8m high on the inner side, 8m high with ditch on the outer, northern, side. The outer northern rampart is 5m wide and 1m high on the uphill, southern, side and 2m high with the ditch on the north side. There is a breach on the north-west side of the outer rampart. The interior is uneven, with only one possible hut site identified (NPRN 509889).

Source: Ordnance Survey 494 Record Card, SO05SE9.

R Hayman, H&H, 24 February 2010.