Dún Dúchathair or simply Dúchathair (anglicized Doocaher), meaning “black stone ringfort”, is a large stone fort on the island of Inis Mór.
Due to erosion, it now sits on a rocky promontory that stretches out into the sea. The fort consists of a terraced walls, reaching 6 metres high and 5 metres wide. On the inside are the ruins of various rooms, possibly from Clocháns or Beehive huts.
There is also evidence of a Chevaux de Frise protecting the entrance. Excavations have not been carried out on the fort so it’s exact dates cannot be given but it is thought to be possibly contemporary with Dún Aonghasa.
It is understood that the name the Black Fort comes from the dark coloured limestone which is characteristic of this particular area on the island.