Castell Gwallter is a medieval castle represented by the earthworks of its motte or castle mound, and of its various baileys or courts. The castle was established by the Anglo-Normans in about 1110 and was the centre for the lordship of Geneu'r-glyn commote. It was destroyed in 1135 and is last heard of in 1153. It may have been replaced by Domen Las, the castle of Abereinion (see NPRN 303600). The castle is some 50m south-west of St Michael's Church (NPRN 400451) and the two may have been contemporary.

The castle mound is a ditched and counterscarped, circular flat-topped mound, 32-33m in diameter and about 4.5m high. It would have been crowned by a great timber tower with a strong breastwork on the counterscarp. There is a small ditched and banked bailey or court on the north side. This is about 38m north-south by 28m, and would have been the site of the lordly hall and associated offices. There are indications of a much larger court on the east side of the motte. This is roughly rectangular with rounded corners, roughly 80-100m east-west by 126-135m, and is defined largely by scarps. Such a large enclosure would suit the dignity of the main castle of a lordship and would have accommodated assemblies of lesser lords.

John Wiles, RCAHMW, 11 February 2008