Built by the O’Flaherty clan around 1500, this formidable stronghold controlled the passage between Lough Corrib and the sea, making it a strategic prize during centuries of conflict. The O’Flahertys, known as the ‘Ferocious O’Flahertys’ by their enemies, ruled western Connacht from this fortress until they lost it to the English in 1572.

The castle’s unusual design sets it apart from other Irish tower houses. It consists of a six-storey tower built on a rocky outcrop, surrounded by the remains of an outer ward that once contained a banqueting hall and other buildings. The tower features murder holes above the entrance, spiral staircases cunningly built to favour right-handed defenders, and bartizans projecting from the corners for dropping unpleasant surprises on attackers. Beneath the castle, the river has carved out a natural cave system; local legend claims these caves once provided a secret escape route during sieges.

After changing hands multiple times through rebellion and confiscation, Aughnanure eventually fell into ruin. The Office of Public Works began restoration in the 1950s, and today visitors can climb to the battlements for views across the Connemara landscape. The castle’s riverside setting, complete with the remains of a boat pier, offers a glimpse into how the O’Flahertys once dominated both land and water routes through this part of Galway, their power base for nearly three centuries of Irish history.