Castell Gwithian, with a possible borough enclosure, was established in 1110 and possibly destroyed in 1116. It is situted some 200m to the east-north-east of St David's Church, Blaenporth (NPRN 308996) and the two are likely to have been contemporary.

The present site, a Scheduled Ancient Monument, rests on steep natural scarps above minor stream valleys. It includes a rather irregular enclosure, measuring some 110m east-west by 85m. which It is otherwise defined by a ditch and rampart, currently much degraded, on the south-west and south. On the east is an oval mound, about 40m north-east to south-west by 37m, and 4.4-7.0m high, having a dished oval summit. 'Brynawelan' occupies a subrectangular area at the foot of the mound, about 32m across, conceivably the site of an inner enclosure.

There are indications of a curvilinear ditched enclosure, about 40m across, set within the eastern part of the enclosed area.

J.Wiles, RCAHMW, 01 March 2004