This castle is spectacularly situated on a rocky headland. The name and the presence of a souterrain suggests that the site was occupied during the Early Christian period. However it was not documented until the 16th century. It is separated from the mainland by a deep ditch, now spanned by a modern bridge. The earliest parts date from the 14th century but most of the castle dates from the 16th century when it was in the hands of the MacQuillans and later MacDonnells.
It was badly damaged in an artillery attack by the English Deputy, Sir John Perrott, in 1584. It was repaired and extended by Sorley Boy and James MacDonnell but was abandoned and fell into disrepair from the later 17th century onwards. The rectangular court on the mainland contains 17th century domestic buildings and leads downhill towards the bridge.
There is a twin-towered gatehouse with Scottish corbelled turrets. It dates from about 1600. There are remains of several round flanking towers dating from the 14th century. Beneath one of these is a rock-cut souterrain.
The courtyard is dominated by a large two-storey hall with bay windows which was built in the early 17th century. Beyond this were service rooms, a kitchen and a lower yard. The rock on which the castle stands is penetrated by a large cave.
