Built by Sir Jasper Harbert, this imposing structure combines defensive features with the comforts of a 17th-century manor house. The Harbert family coat of arms still adorns the space above the two-centred arch doorway of the entrance tower, accompanied by their motto ‘By God of might, I hold my right’. The entrance itself shows fascinating defensive details: pronounced pocked dressing on its surface, a yett hole on the right-hand side for securing a heavy iron gate, and a machicolation directly overhead at wall walk level, from which defenders could rain down unpleasantries on unwelcome visitors.

The castle’s interior reveals a sophisticated layout designed for both security and domestic life. The entrance tower, measuring roughly 6 by 5 metres internally with walls a metre thick, served as a reception area and featured three large fireplaces, each with its own tall chimney stack. From here, a large winding staircase, now reduced to masonry supports along the north wall, once provided access to the upper floors. The main rectangular block contains four barrel-vaulted rooms at ground level, their ceilings still showing remarkable evidence of the original wickerwork centring used during construction. One of these chambers likely served as the kitchen, complete with a fireplace whose flue protrudes beyond the external west wall. A now-blocked mural staircase in the south wall once led to the upper storeys, where wooden floors, large fireplaces, and grand transomed and mullioned windows created comfortable living quarters for the Harbert family.

The castle’s defensive capabilities are evident throughout the structure. Musket loops pierce the north wall of the main tower and the south wall of the entrance tower, whilst a bartizan projects from the northeast corner, providing an elevated defensive position. Evidence of a bawn wall can be traced along the southeast and east walls of the main tower, and to the south stands the gable end of what appears to have been a guardhouse with its own wall walk, originally forming part of a range of buildings within the protected bawn area. This combination of residential grandeur and military practicality makes Ballycowan Castle a fascinating example of how Ireland’s landed gentry balanced comfort with security during the turbulent 17th century.