Leap Castle is reputedly one of the most haunted castles in Europe. Originally an O'Carroll family residence, the 1514-built castle was the scene of many dreadful deeds and is famous for its eerie apparitions – its most renowned inhabitant is the 'smelly ghost', a spirit that apparently leaves a lingering odour after sightings. Another apparition is the self-explanatory 'red lady'.
Renovations are ongoing, but you can arrange a visit. It's 12km southeast of Birr.