Fraoch Eilean Castle is a 13th century stone hall house and courtyard fortress, founded by the MacNaughtons. The rectangular hall stands at the eastern end of a north-eastern plateau on Fraoch Eilean and its western ancillary buildings were of turf and timber. Later the courtyard was encased by a stone curtain wall, with a southern gateway and a flanking south-western round angle tower. In the early 17th century the hall house was re-occupied, when a small dwelling house was built within its north-east corner. The remaining roofless walls were use as an inner courtyard and in the late 17th century, the house was extended across the eastern part of the hall but by the mid 18th century the island had been abandoned. 2 miles north-east at Dalmally is Kilchurn Castle.