Dating back to at least 1574, when records show it housed the Derby O’Shaghnes family, this three-storey defensive structure rises approximately 13.5 metres in diameter from its gently sloping base. The rendered walls conceal a sophisticated medieval security system; visitors entering through the east-northeast facing double doorway would first pass through a round-headed outer arch, then a pointed inner arch still bearing the vertical grooves that once guided a protective portcullis.

The ground floor reveals the careful planning that went into these defensive residences. Beyond the entrance lobby, three doorways lead to different sections: a northern guardroom complete with fireplace and arrow-loop, a southern passage to both rubble-filled intramural and spiral staircases, and a western entrance to the main subrectangular chamber. This principal room features splayed arrow-loops set deep within embrasures at strategic points around its perimeter. The first floor, once supported by wooden beams evidenced by surviving corbels, housed the mechanism for raising and lowering the portcullis, whilst a stone vault separates it from the second floor above.

The upper levels showcase both defensive and domestic features typical of late medieval Irish tower houses. The second floor’s main room includes what was likely a garderobe accessed through a southern opening; its blocked exit chute remains visible on the exterior wall. A small northeastern chamber would have provided access to machicolations positioned above the main entrance, though only the supporting corbels survive today. The upper floor windows display elegant ogee-headed single lights with recessed spandrels, with one second-floor example featuring a hood-moulding that bends outward and tapers, terminating in carved interlace ornament. Arrow-loops continue to light the spiral staircase throughout the structure’s height, whilst remnants of the original bawn wall extend eastward, hinting at the larger defensive complex that once surrounded this impressive tower.