The Black Fort stands on a dramatic coastal promontory at the southeastern end of Inis Mór, less visited than Dún Aonghasa but arguably more atmospherically situated. The fort takes its name from the dark limestone of which it is built, and the walls — up to four metres thick in places — close off the neck of a cliff-edged headland with the sea crashing on three sides.
The walk to Dún Dúchathair from the road takes about fifteen minutes across open karst limestone, and the isolation from other tourists makes it feel different from Dún Aonghasa: quieter, more exposed, more genuinely prehistoric. The views along the island's southern cliffs are excellent. This is a place where the Atlantic makes its presence felt — wind and spray on all but the calmest days.