St Mary's, founded in 1168 by Donal Mor O'Brien, the last King of Munster, is the oldest building in Limerick still in continuous daily use. The cathedral has been added to in every century since: a Norman nave, a late-medieval chapter house, a 17th-century tower with a peal of bells, and a 19th-century reredos. The result is layered rather than unified, and the building rewards a slow walk around the interior.
The medieval misericords in the chapter house are the single thing not to miss — Ireland lost most of its carved-wood ecclesiastical furniture to the Reformation and to Cromwell, and these 23 stalls are essentially unique. The bell-ringers practise on Friday evenings, and the cathedral choir sings Evensong on Sunday afternoons; either gives the building a sound that a quiet daytime visit cannot.