Just outside Killarney Town, this 15th-century fortress still guards the edge of the Lower Lake. Built by the O’Donoghue chieftains, the castle was the last stronghold in Munster to surrender to Cromwell’s forces in 1652. But it could not withstand time and the English army: All that remains of it today is a tower house surrounded by a fortified bawn (walled garden) with rounded turrets. The tower has been furnished in the style of the late 16th and early 17th centuries. The tours are a little overlong for the amount of worthwhile information there actually is to impart, but unfortunately it’s the only way of seeing inside. However, you can wander the grounds at leisure. In good weather, the best way to reach the castle is via a lakeside walk (it’s 3km/2 miles from Killarney). From the castle, you can also take boat tours of the lake.