See all Attractions in Dun Laoghaire Dun Laoghaire for: Adventure, Food And Dining, Art And Culture, Nightlife, Spa, History, First Timers, Family, Romance, Shopping Monkstown Castle Monkstown About Monkstown Castle, Monkstown (just NW of the center of Dun Laoghaire). The ruins of an old castle is right next door in Monkstown, a walking distance from the centre. It was built in 1636 and is in the middle of a residential area. free. Add to Wish List