Dunlough Castle, also known as Three Castle Head or Dún Locha (meaning “fort of the lake”), sits at the northern tip of the Mizen Peninsula in County Cork. Perched on cliffs overlooking the Atlantic, it commands a dramatic, remote coastal site. The ruins occupy a narrow isthmus linking the rocky promontory called Three Castle Head with the mainland, and are only accessible by foot via private farmland to the south.

The castle was originally founded in 1207 by Donagh O’Mahony, a chieftain of the O’Mahony clan, during the period in which Norman influence was expanding in southern Ireland. Over time, the O’Mahony family retained possession of Dunlough for several centuries, until it was confiscated by the English crown in 1627.

Architecturally, Dunlough Castle is unique: it consists of three rectangular stone towers linked by a long curtain wall spanning from the cliffs to the shore of a lake. Part of this wall also functioned as a dam, retaining the lake’s water and preventing it from spilling over the cliff into Dunmanus Bay below. The structure was built using dry stone masonry (without mortar), which contributes to its gradual decay. Because of the natural defenses—cliffs on one side, the lake on the other—and the built fortifications, Dunlough must have been formidable, though there is no known record of it ever being attacked.