Built by the O’Sullivans of Formoyle and Ballycarna, a branch of the prominent O’Sullivan clan, this modest stronghold once stood three storeys tall, though only two levels survive today. The rectangular structure, measuring 11 metres by 8.44 metres, rises from a battered base to an average height of 5.1 metres, its walls constructed from coursed rubble bound with remarkably durable gravel and lime mortar.

The castle’s defensive features reveal the careful thought that went into its construction. The original entrance, now marked by a ragged gap in the eastern wall, was once a formidable barrier; the doorway was fitted with both a wooden door secured by drawbars and an outer iron grille that swung on hinges, three housings for which remain visible in the northern jamb. Beyond this entrance, a lobby led to various chambers and a circular stairwell tucked into the northeast corner. The ground floor’s main chamber was illuminated by narrow loops with splayed openings, many still showing the pivot holes and sockets for wooden shutters. Above, the first floor likely featured a murder hole positioned over the entrance lobby, allowing defenders to attack intruders who breached the outer defences.

The internal layout followed a practical design common to Irish tower houses of the period. Each floor consisted of a main chamber separated by a cross wall from smaller rooms and the stairwell area. The floors were supported by rough corbels projecting from the side walls, whilst built-in wall cupboards provided storage throughout. Though time has taken its toll, particularly on the northeast corner which has been significantly undermined, enough remains to appreciate the building’s original form. During excavations, archaeologists discovered a jews’ harp lodged in an interstice of the eastern wall; this small musical instrument, now housed in Kerry County Museum, offers an unexpected personal touch to these ancient stones.