Greenan Castle was originally a 12th century earthwork and timber fortress, founded by Roger de Scalebroc. Built on the edge of a sheer coastal cliff, wide ditches with a counterscarp bank cut across the promontory, making inner and outer wards. The Davidson family, owned the stone fortalice which stood here in the 15th century but in the early 17th century, it was absorbed when John Kennedy of Baltersan constructed the rectangular tower house. Of three storeys and a garret, the tower was crowned with crow-stepped gables, three corbelled angle turrets and on the north-west angle, a caphouse and stair-head. The original entrance was at first-floor level but a second entrance has been cut through the chamfered base-plinth, into the vaulted basement. To the fore, a mortared rubble wall, does not appear to be contemporary and could be remains of an earlier hall-house and a barmkin wall. 2 miles south-east is Newark Castle and 10 miles north-east is Tarbolton Motte.