Fraoch Eilean Castle is a 14th century stone keep and courtyard fortress, founded by occupies a strong defensive position on the plateau summit of the NE eminence of Fraoch Eilean. The existing remains appear to comprise work of four main periods, of which the earliest may be ascribed to a date within the 13th century, at which time a substantial stone hall- house was erected towards the E end of the site, the remaining area of the plateau being used for the construction of ancillary buildings of turf and timber. At some later date within the medieval period this remaining western portion of the summit was enclosed by a stone curtain-wall incorporating an entrance-gateway on the S side and a round tower at the SW angle. The hall-house became derelict, but was re-occupied about the beginning of the 17th century, a small dwelling-house being constructed withing its NE corner, the remaining, roofless part of the hall-house being adapted for use as an inner courtyard. A final reconstruction took place some time in the later 17th century, when the small house was enlarged to take in the SE corner of the hall-house as well. It appears to have been abandoned some time before 1769 and the walls of the hall-house now stand to an average height of about 4.6m, the N wall, however, which is founded at a lower level than the remainder, survives to a height of some 9.0m.