Image by Peter Unger Getty Images
One of Europe's best-preserved star-shaped artillery forts, this vast 17th-century fortification would be worth a visit for its spectacular views alone. But there's much more here: the 18th- and 19th-century ruins inside the walls make for some fascinating wandering. It's 3km southeast of Kinsale along the minor road through Scilly; if you have time, hike there along the lovely coastal Scilly Walk.
Built in the 1670s to guard Kinsale Harbour, the fort was in use until 1921, when much of it was destroyed as the British withdrew. Displays explain the typically tough lives led by the soldiers who served here and the comparatively comfortable lives of the officers.