Castle Donovan, also known as Castledonovan or O'Donovan's Castle, is the remains of an Irish tower house located near Drimoleague in County Cork. It was once the seat of the Clann Cathail sept of the O'Donovans during the 16th century. The castle, originally named Sowagh, stands about 60 feet tall on a large rock by the River Ilen. Legend has it that the tower was damaged by Oliver Cromwell's soldiers in the 1640s and has been uninhabited since. Despite its rugged history, efforts have been made to conserve the structure, making it a listed National Monument today.