Boyle Abbey is the reason many travelers first notice the town. The Cistercians founded it in the twelfth century, and the remains still show a large church, heavy Romanesque arches, later Gothic work, and the outline of a serious monastic complex.
It is not a manicured ruin with every gap tidied away. That is part of the appeal. You can still read the ambition of the building in the thick stone and long nave, while the broken parts make it feel properly old rather than staged.