Dún Briste, Downpatrick Head, Co. MayoIn 1393, the Atlantic separated this stack from the mainland. You can still see traces of buildings on its summit. Nobody has stood up there in centuries. Dn Briste translates as "the broken fort," and from the cliffs at Downpatrick Head the name makes immediate sense. This massive column of layered sedimentary rock rises fifty metres from the ocean, its top flat and green, as if someone lifted a small field and set it on a pillar of stone. It looks