Located on the south-east slopes of Mynydd Maen are the footings of an "L"-shaped building. It has a sub-divided north-south range, c.17.3m by 7.75m, with a c.14m (east-west) by 7.6m chamber on the north of the east side.
The site associated with a medieval chapel, and now scheduled as such. It was once a very important stopping point on the Pilgrims’ route to Penrhys. The chapel was dedicated to St Derfel, one of only two in Wales – the other being in Merionydd.
D.Leighton & T. Driver, RCAHMW, 5 October 2015