This oblong tower house, dating from around the mid-fifteenth century, measures approximately 14 metres by 9 metres and originally rose five storeys high. The main wing featured four wooden floors topped by a stone vault, whilst the end wing housed a spiral staircase providing access to each level. Though time has claimed the southern face and much of the side walls, the remaining structure still displays distinctive medieval features including skew-loops positioned at strategic angles, numerous ambries, and window slits with elegant ogee-headed designs.

The castle sits within a compact rectangular bawn; a fortified enclosure measuring roughly 19 metres east to west and 25 metres north to south. The defensive walls, which narrow from 1.8 metres thick at the base to 0.9 metres at the top, originally featured four D-shaped turrets at each corner, each about 3.65 to 5 metres in diameter. Whilst the south wall and southwest turret have been reduced to ground level, three turrets survive, with one still retaining its vaulted roof and defensive gunloops. This combination of tower house and bawn represents a typical late medieval Irish fortification, designed to protect the resident family and their immediate household from the frequent raids and conflicts of the period.

By the mid-seventeenth century, the Civil Survey of 1654-56 recorded the castle as already ruined, though still in the possession of Richard Stephenson of Dunmoylan, described as an Irish Papist. The Ordnance Survey Letters later dismissed it simply as “a ruin on a plain,” but closer examination reveals a complex defensive structure that would have been both an imposing residence and a practical stronghold. Today, Garraunboy stands as one of many tower houses dotting the Irish landscape, each a testament to the turbulent centuries when local lords required fortified homes to maintain their holdings and protect their families.