Built from limestone rubble with well-cut quoins and a distinctive base-batter, the structure measures approximately 12.85 metres north to south and 10.45 metres east to west. When surveyed in 1654-6 during the Civil Survey, it was already described as ‘an old Castle that wants repayre’, owned at that time by John Cantwell of Mockarky, identified as an ‘Irish Papist’, giving us a glimpse into the religious tensions of 17th-century Ireland.

The castle’s defensive architecture is particularly impressive, featuring a murder-hole protecting the main entrance on the west wall, accessed by stone steps built on additional masonry support. Inside, a complex system of mural stairs winds through the walls, beginning along the west side before spiralling at the southwest angle. Each floor reveals different architectural features: the ground floor contains guardrooms and wall cupboards; the first floor, once supported by wooden beams on stone corbels, has large window embrasures with blocked flat-headed windows; whilst the second floor boasts a joggle-jointed fireplace and barrel-vaulted ceiling. The upper levels, though now largely inaccessible due to collapsed wooden stairs that once replaced the broken stone steps, display elegant ogee-headed windows typical of medieval Irish architecture.

At parapet level, the castle’s military features become even more apparent, with remains of machicolations positioned strategically over the entrance and garderobe chute, plus bartizans at the northeast and southwest angles supported by corbels. Later additions tell their own story; a small 18th or 19th-century building was attached to the tower’s west wall, and nearby foundations reveal the location of Suir Castle house, a ‘splendid mansion’ built by Lord Baron Massy in the 18th century, now reduced to fragmentary ruins. The remains of what may be a bawn wall or later revetment runs along the precipice edge northwest of the tower, adding another layer to this site’s complex architectural history.