This fortress of the O’Sullivan clan, reputedly built by Dermot O’Sullivan around 1540, consists of a tower house set within a rectangular bawn, or fortified courtyard. The tower’s remains are most substantial in the southwest corner, where the west wall stretches 10.3 metres wide and the north wall extends 12 metres, both standing four storeys tall. Inside, you can still trace the ghostly outlines of segmental vaults that once supported the first and third floors, running east to west. The west wall features central window openings at each level, including a particularly interesting first floor embrasure flanked by mural passages and a graceful ogee-headed window on the third floor.

The bawn itself forms an irregular rectangle measuring 26 metres north to south and 48 metres east to west, with its southern face dramatically overlooking a rock-cut gorge. Dating likely to the 17th century, this defensive enclosure shows sophisticated military architecture with projecting towers at each corner; the northeast and southeast corners feature acutely angled towers reminiscent of bastions on star-shaped forts, whilst the northwest tower takes a blunter point and the southwest forms a rough rectangle. The western walls bristle with gun loops, and rather charmingly, the southwest tower incorporates four tiers of nesting boxes on each face at first floor level, suggesting the castle’s defenders may have kept pigeons for food or messaging.

The castle’s history intersects with one of the most dramatic episodes in Irish history; it surrendered following the fall of Dunboy Castle in 1602, marking the end of O’Sullivan resistance during the Nine Years’ War. Today, whilst the eastern half has been modified to accommodate now-disused farm buildings, the remaining structure offers a remarkable glimpse into the defensive architecture and daily life of a Gaelic lordship. Archaeological excavations in 2002 and 2004 have added further layers to our understanding of this evocative ruin, where bartizans still crown the corners and centuries-old stonework continues to defy time.