Situated 80 meters from the Irish shore is an impressive sea stack known as Dun Briste or the ‘Broken Fort’. It is an astonishing formation in the sense that it allows you to see layer upon layer of multicolored rock strata. The cliffs in the area, including the stack were formed in the Lower Carboniferous period, a geological term applied to a period about 350 million years ago, when sea temperatures around Ireland were much higher than today.
Dun Briste was cut off from the mainland by the sea in 1393, and according to a passage in the annals by MacFirbis the people living on the cliffs had to be rescued by ship ropes. Local folklore tells a different story though. Legend has it that a pagan chieftain once lived on the spot where the stack stands. When he refused to convert to Christianity, St. Patrick struck the ground with his crozier, splitting a chunk of the mainland into the ocean, with the chieftain on top.
Nevertheless, the first story seems to hold more truth. A few years ago, a helicopter landed several scientists on the stack; they were the first humans to set foot there for ages. They stayed there overnight and examined the surface where they found the remains of a medieval house, walls, cultivation ridges, and a corn grinding stone.
via Castlebar News