A dramatic 150-foot-high limestone outcrop, the famous Rock of Dunamase dominates the landscape east of Portlaoise. For this reason, it was used as a military stronghold. As far back as AD 140 its occupants kept watch against marauders, and it was fought over in turn by the Vikings, Normans, Irish, and English. Today it's crowned by the ruins of a 12th-century castle, once home to Diarmuid MacMurrough, king of Leinster, who precipitated the Norman invasion when he invited
the famed and feared Norman leader Strongbow to Ireland to marry his daughter. Some of the castle's thick walls still stand. The main reason for visiting the Rock today is to take the short walk to its summit to enjoy the view of the Slieve Bloom Mountains to the north and the Wicklow Mountains to the south.
N80 (Stradbally Rd.), 5 km (3 mi) east of Portlaoise, Portlaoise, Co. Laois, Ireland