Holy Cross Abbey was a Cistercian monastery in Holycross near Thurles, County Tipperary, Ireland, situated on the River Suir. It takes its name from a relic of the True Cross or Holy Rood. A supposed fragment of the True Cross was brought to Ireland by the Plantagenet Queen Isabella of Angoulême, around 1233. She was the widow of King John and best…Holy Cross Abbey was a Cistercian monastery in Holycross near Thurles, County Tipperary, Ireland, situated on the River Suir. It takes its name from a relic of the True Cross or Holy Rood. A supposed fragment of the True Cross was brought to Ireland by the Plantagenet Queen Isabella of Angoulême, around 1233. She was the widow of King John and bestowed the relic on the original Cistercian Monastery in Thurles founded in 1169 by King Donal O'Brien of Thomond, which she then rebuilt.