Built around 1440-1480 by Donnchad MacNamara, this rectangular tower house measures roughly 11.2 metres north to south and 7.5 metres east to west. The structure, constructed from roughly squared and coursed limestone with a distinctive base batter, remained in MacNamara hands until 1641 when it passed to Philip Bigoe. The castle’s history took an unusual turn in the 1840s when it served as a fever hospital, likely due to its proximity to the Tulla Union Workhouse just 640 metres to the southwest.

The tower house retains many of its original defensive features despite extensive ivy coverage and later modifications. The main entrance in the south wall features a pointed cut-stone arch with chamfered surrounds and a yett-hole for securing the door. Inside, the entrance lobby opens into three directions through pointed doorways, including access to a small guardroom with a wicker-centred vault and the main ground floor chamber. A spiral staircase, turning clockwise from the western doorway, originally provided access to the upper floors. The ground floor shows evidence of later subdivision, probably dating from its conversion to domestic use and subsequently to a hospital, whilst the first floor retains traces of its original window embrasures and a decorated limestone fireplace mantel bearing carved writing and a wagon wheel motif.

Today, the castle presents a complex architectural puzzle, with 19th-century modifications overlaying its medieval fabric. The south and north walls were converted to gables during this period, and a single-storey structure was added against the north wall. Various blocked openings, modified embrasures, and consolidated wall tops tell the story of a building that adapted to changing needs over five centuries. The extremely tall chimney flue rising from the east wall and the remnants of plasterwork at various levels hint at the comfort improvements made when the fortress transformed into a residence. Despite these alterations, the essential character of this late medieval tower house remains legible in its thick walls, narrow loops, and defensive entrance arrangement.