Although the remains of Dunoon Castle are scant, its hilltop position affords stunning views of the town of Dunoon and the Firth of Clyde. Originally built in the 12th century, was once an important stronghold and even served as a royal residence in the 14th century. It originally consisted of three circular towers in a triangular formation but little of the structure remains today. Abandoned in the 17th century after being invaded, it fell into ruin soon after with its stones quarried to build the 19th century Castle House.