The rectangular structure, which measures 8.5 metres long by 5.5 metres wide, was built with randomly coursed limestone blocks and features a distinctive D-shaped stair tower projecting from its northwestern wall. Once associated with a Preceptory of the Knights Hospitallers, the castle later played a role in defending the Pale, the fortified boundary that protected the English-controlled area around Dublin from the Gaelic Irish territories beyond.

The tower’s interior reveals sophisticated medieval construction techniques, with a barrel-vaulted basement and another vault over the fourth floor. Each of the building’s five levels served different purposes; the basement, accessed through a doorway in the southwestern gable wall, contains wall cupboards and a stone drain, whilst the upper floors feature fireplaces, wall cupboards, and rectangular windows set in large embrasures, some complete with window seating. A narrow spiral staircase within the projecting tower connects all floors, lit by seven arrow loops strategically positioned to provide both illumination and defensive coverage. The castle adjoins a gatehouse at its southwestern end, with interconnecting doorways allowing movement between the two structures at multiple levels.

Archaeological investigations in 2005 and 2006 uncovered medieval pottery sherds about 80 metres from the monument, including Leinster cooking ware and both coarse and fine Dublin-type ceramics, providing tangible evidence of daily life at this defensive outpost. The building has undergone restoration work, with the stone-slabbed roof, guttering and crenellations repaired, whilst the chimney stacks have been lowered and capped below the battlements’ height. Today, this National Monument stands as a well-preserved example of late medieval Irish tower house architecture, its thick walls and defensive features testament to the turbulent times when the English colonists and Gaelic Irish vied for control of the fertile lands of County Kildare.