Athlone Castle stands on the west bank of the Shannon, where it has commanded the ford since 1210. King John ordered its construction as part of an effort to consolidate English control over the Irish midlands, and the site has been fought over in almost every significant conflict in Irish history — most dramatically during the Williamite War of the 1690s, when it was the pivot point of the Jacobite defence of Connacht.
The interior has been rebuilt as a visitor centre that covers the castle's military history, the town's development, and the life of John McCormack, the great Irish tenor who was born in Athlone. The exhibits are well-presented and worth an hour. The views from the ramparts take in the Shannon, the Church of Saints Peter and Paul with its twin copper domes, and the rooftops of the old quarter. Open Tuesday to Sunday; closed Monday except in peak summer.