Ennis friary (or Abbey, as it's generally known) was the catalyst for the town's beginning, and so it isn't a bad place to start. There is an entrance fee, but it's very modest, and the staff will let you borrow the guide brochure while you walk around.
The buildings are mainly in ruins, but the surviving stone artifacts give clues to the history of the town. The early, imposing tombs belong to the O'Briens (founders of the friary and descendents of the great Brian Boru) and to the other principal medieval family of the area, the MacMahons. Then come the fascinating carvings, starkly devotional of Saint Francis and the "Ecce Homo" - Christ before Pontius Pilate. After the Reformation, the building was used as a court and Protestant church, and the later memorials are to the English settler families who then dominated the town.
But the site is more than the church itself; traces of the original ranges - dormitory, kitchen, workshops still remain and part of the cloister has been reconstructed to give the imaginative an idea of what the friary must once have been, when it dominated the life of the town.