The tower house presents an unusual architectural puzzle; at 45 feet long externally but only 12 feet wide internally, it’s remarkably narrow for a defensive structure. What remains today are fragments of the northeast and southwest walls, built from uncoursed rubble limestone, with the northeast wall still reaching about 4 metres in height. The most intriguing feature is a rectangular projection at the northeast corner that transitions to a rounded form as it rises, whilst a large splayed opening at first floor level hints at the castle’s former domestic arrangements.

The castle’s defensive capabilities extended well beyond its peculiar tower house. A substantial bawn wall, roughly 12 feet high and pierced with gun loops, once enclosed an irregular courtyard that may have been octagonal in shape. Archaeological surveys from 1994 revealed that this bawn stretched approximately 65 metres northeast to southwest and 41 metres northwest to southeast, with the wall changing direction sharply at several points. Four gun loops remain visible, strategically positioned at angles where the wall shifts direction, suggesting careful planning for defensive crossfire.

The entire complex was originally surrounded by a deep fosse, adding another layer of defence to this stronghold. According to the Victorian antiquarian Carrigan, who documented the site in 1905, the west wall had been reinforced with an additional wall of equal thickness built against its exterior, perhaps indicating structural concerns or enhanced fortification needs. Today, visitors can still trace sections of the bawn wall running south from the tower house for about 50 metres, complete with evidence of a wall walk where defenders once patrolled. The townland name itself, Ballygeehin, derives from ‘the Town of O’Gihin or O’Gahan’, preserving a memory of even earlier inhabitants before the Fitzpatricks claimed this strategic position in the gently rolling Laois countryside.