What remains today is a far cry from the substantial complex that once stood here; the OS Namebooks from the 19th century noted ruins with part of one tower still standing, though even that has since been levelled. In the 1930s, local historian O’Toole managed to document what was left, describing a tower fragment about 12 feet high with impressively thick walls measuring 5 feet across. He also spotted telltale signs of the castle’s former extent in the nearby farm buildings, where medieval features like a splayed window had been incorporated into later structures. This particular window, with its characteristic defensive design, narrowed from 2 feet 10 inches on the inside to just 1 foot 8 inches on the outside through a 3-foot-thick wall.

The castle’s former importance becomes clearer when examining historical records. The Down Survey map of 1655–6 shows both a castle and a mill downstream, indicating this was once a working estate rather than just a defensive structure. Perhaps most intriguingly, Thomas Dineley’s 1680 sketch reveals what visitors would have seen in the late 17th century: a complex of buildings dominated by two tall, square, gabled towers. Curiously, Dineley’s drawing shows no obvious fortifications, suggesting the castle may have already transitioned from military stronghold to comfortable residence by that time.

Today, visitors to Ballynunnery will find little evidence of this once-prominent castle. The tower that O’Toole photographed in the 1930s has been demolished, and the outbuildings he described have likely been further altered or removed. What was clearly a substantial medieval building complex, significant enough to warrant inclusion on multiple historical maps and sketches, has largely vanished from the landscape, leaving only documentary evidence and archaeological records to hint at its former presence.