The tower house, which once stretched five storeys skyward, now retains only its lower three levels after the upper floors were demolished in the 1950s. Built from roughly coursed sandstone rubble, the structure features the classic defensive elements of a medieval Irish tower house, including a base batter, pointed doorway with yett-hole, and the rather sinister murder-hole positioned above the entrance lobby.

The castle’s documented history begins in 1508 when the Lord of ‘Cowellqueyle’ appears in records as a suitor to the Earl of Ormond. By the time of the Civil Survey in 1654-56, the property belonged to one ‘Morish Stoke of Coolequiell Irish Papist’ and was described as ‘a good castle yett wanting repayre’. The survey noted the presence of a bawn and thatched house alongside the tower, suggesting this was once a more extensive fortified complex. Indeed, archaeological evidence points to a possible motte 560 metres to the east and a deer park immediately adjacent, indicating the site’s medieval importance.

Today, the castle presents a study in architectural decay and adaptation. The interior preserves vaults over the ground and second floors, whilst a complex arrangement of mural stairs winds through the thick walls, originally providing access to all levels. Each floor was lit by carefully positioned windows, some featuring decorative ogee heads, whilst garderobe chambers built into the southeast wall and south angle provided necessary facilities. Later modifications include a T-shaped house built against the northeast wall and various attempts at buttressing that have themselves begun to fail. The structure faces serious stability issues; the northwest wall bears a large hole and significant cracking caused by the later insertion of a fireplace, whilst the south angle collapsed entirely in February 2021. Despite its precarious state, Coolquill Castle remains a fascinating example of how these defensive structures evolved from military strongholds to domestic residences, each modification adding another layer to its complex story.