The "Rock" of Dunamase (dun-a-mace) located near modern Portlaoise (port-leash) in County Laois is of central importance to the history of Medieval and early-Modern Ireland. The castle-keep, begun in 1170 CE, was part of the Anglo/Norman pale extending out from Dublin and the stronghold of Richard FitzGilbert de Clare (a.k.a. "Strongbow") who spearheaded the Anglo-Normanin invaision of Ireland. By the Fourteenth Century it passed into Irish hands and remained a center of military and political importance until destroyed in the invasion of Oliver Cromwell 1650.

The stategic significance of the site is obvious to visitors as the hill upon which the castle was built rises 200 feet above the surrounding plain providing defenders a 360 degree view of the plain.