Originally known as Kilvoynell when it was held by Myles Mac Evilly in 1574, the castle later passed into the hands of Theobald Bourke, better known as Tibbot-na-Long, who was the son of the legendary pirate queen Granuaile (Grace O’Malley). The rectangular tower, measuring 9.5 metres north to south and 12.6 metres east to west, sits within the southwest corner of what was once a substantial bawn, complete with defensive turrets in the northeast and southeast corners that still display their gun loops.

Though time has taken its toll on the structure, with much of the southern and eastern walls having collapsed, the remaining architecture reveals sophisticated medieval construction. The tower’s ground floor entrance, located at the eastern end of the north wall, opens into two chambers divided by a wall that originally extended up to the first floor. A complex system of stairs once provided access throughout the building; mural stairs on the south side led to the first floor, where a spiral staircase began its ascent to the upper levels. Each floor showcases finely cut pointed doorways, particularly notable at first-floor level where three such doorways grant access to the main chamber and two mural chambers, one featuring a lintelled roof on the west wall, the other with a pointed vault on the south.

The upper floors follow a similar layout, with the second floor containing a main chamber with remnants of vaulting, a mural passage leading to a garderobe, and another vaulted mural chamber. The spiral stairs terminate at the third floor, though they may have originally continued higher, and a small room here contains blocked stairs that likely once provided access to a wall walk. The main chambers throughout the tower were well lit by large windows, a luxury that speaks to both the wealth and confidence of its builders. Today, portions of the defensive bawn walls survive alongside the tower, with later ancillary buildings constructed along the southern wall adding layers to the site’s long history.