Photo ©Paul R. Davis

There are the remains of an Iron Age hillfort and a medieval castle on the summit of Carn Fadryn, a 1200 feet high mountain on the Llyn peninsula. The top is defended by the remains of two strong stone walls which form an inner fort of twelve acres and a larger fort of 26 acres. On the highest part of the summit a narrow platform of rock was utilised as a ready made motte. The castle was first mentioned by Gerald of Walesin 1188 as having been newly built along with Castell Deudraeth, Dinas Emrys, Tomen Castell and Castell Pen-y-garn. There are no traces of any internal buildings surviving.