Today, only fragments of this once-imposing structure remain; the south wall of the tower and its adjoining bawn still stand, along with a circular corner tower at the northwest angle. Built from uncoursed limestone rubble, these ruins offer a glimpse into the turbulent period of Irish history when such fortifications were essential for survival.

The castle’s few surviving architectural details tell us something about daily life within its walls. Two fireplace openings, one at ground level and another on the first floor, mark where the inhabitants would have gathered for warmth, with the chimney stack still visible protruding from the external wall. The northwest corner tower features several musket loops, narrow openings through which defenders could fire upon attackers whilst remaining relatively protected. These defensive features suggest the castle was designed with both comfort and security in mind, typical of fortified houses from this period.

Historical records suggest the castle may have been constructed by Peter Salconstall, who received a land grant here in 1622 during the plantation of King’s County, as Offaly was then known. The design appears similar to Kilcolgan Castle, another fortified house in the county, indicating a regional architectural style that balanced domestic needs with military requirements. Though time and weather have taken their toll on Killooly Castle, these ruins remain an evocative reminder of Ireland’s contested past, when even homes needed to be built like fortresses.