Dunure Castle is a battered coastal ruin above the little harbour village of Dunure, about five miles south of Ayr. It was one of the Kennedy strongholds on the Carrick coast, and the site has exactly the drama you want from a ruined Scottish castle: broken walls, sea wind, a rocky headland, and views across the Firth of Clyde.
The castle is open as a ruin rather than managed like a staffed attraction, so take care around uneven ground and exposed edges. It is best reached by car, bike, or a coastal excursion from Ayr. Combine it with the harbour, beach, or a longer run down toward Culzean Castle.