Even if you have only a few hours to explore Inis Mór, rent a bike (next to the pier) and head straight for Dún Aengus, one of the finest prehistoric monuments in Europe, dating from about 2000 BC. Spectacularly set on the edge of a 300-foot-tall cliff overlooking a sheer drop, the fort has defenses consisting of three rows of concentric circles. Whom the builders were defending themselves against is a matter of conjecture. From the innermost rampart there's a great view of the island and the Connemara coast. In order to protect this fragile monument from erosion, you should approach it only through the visitor center, which gives access to a 1-km (½-mile) uphill walk over uneven terrain—wear sturdy footwear.
7 km (4 miles) west of Cill Ronáin (Kilronan), Kilmurvey, Ireland