This tower house has a colourful history that reflects the turbulent politics of 16th and 17th century Ireland. In 1574, it belonged to Dermot O’Brien and later passed to his son Mahon. When Mahon rebelled against English rule and was killed in 1586, the castle changed hands dramatically; it was leased to Englishmen, first Thomas Cheyny and then John Bealinge. The castle saw further action when it was plundered by O’Donnell in 1599, and by 1641 James Darcy had given it to Murrough O’Brien, Earl of Inchiquin, whose family retained ownership and rented it out until at least 1699.

Today, only the central ground floor of this once-imposing tower house survives, measuring roughly 10.5 metres east to west and 7.6 metres north to south. The eastern wall remains the most intact feature, preserving a pointed arched doorway with elegant architectural details including a chamfer, a bar-slot, and a particularly fine hanging-eye carved in the shape of an inverted cone. This doorway would have led into the main ground floor chamber, which measured 7.2 by 4.7 metres. Visitors can still spot remnants of a guardroom to the north of the entrance and six ivy-covered steps of what was once a spiral staircase at the southeast corner. The eastern half of the vaulted ceiling over the main chamber also survives, showing wicker centring marks in its flat-arched doorway embrasure.

Built from large, dressed limestone blocks laid in irregular courses with slightly battered bases, the castle walls were once 1.5 metres thick. The northern wall includes a garderobe shaft, whilst much of the western wall has collapsed and become overgrown, surrounded by a grass-covered mound about 13 metres in diameter. Many of the castle’s stones have found new life in nearby farm sheds, including a beautifully decorated ogee loophead that once graced a narrow window, now incorporated into a gable wall. The site appears on historic Ordnance Survey maps from 1842 and 1920, where it’s marked as ‘Cloonselherny Castle (in ruins)’, suggesting it had already fallen into disrepair by the mid-19th century.