Built around 1453 by the Mac Richard Butler family, this four-storey tower house was constructed during the same year that James Butler, the 4th Earl of Ormond, died; a marginal note in a medieval manuscript records that the Earl built “the two castles of Thurles” in 1452. The castle originally stood within a defensive bawn, or fortified courtyard, complete with stone walls, angle towers and a gateway, though only fragments of these outer defences remain today. During the tumultuous years of the Irish Confederate Wars, the castle was described in the Civil Survey of 1654-6 as “a faire house wherein the Lady of Thurles liveth with a castle and severall Turrets upon the Bawne”, before Parliament forces captured and partially demolished it.

The tower house itself is a masterclass in medieval defensive architecture, built from coursed limestone rubble with a pronounced base batter for additional strength. Its original entrance on the eastern wall led through two lobbies protected by murder holes overhead and a cruciform gun loop; a defensive arrangement that would have made any unwelcome visitor think twice. Inside, a barrel vault covers the ground floor whilst a pointed vault spans the second floor, with the remaining levels originally supported by wooden floors. A mural staircase winds through the western and northern walls, connecting all four storeys. The third floor, clearly the principal chamber, features elegant two-light ogee-headed windows with cusped decoration and carved spandrels, alongside practical amenities like wall cupboards, a slop stone, and garderobes with chutes descending to lower levels.

Though much altered over the centuries, including a stint as an abattoir that left the ground floor concreted and fitted with a plastic barrel roof, the Black Castle remains a remarkable survivor from medieval Ireland. The southwestern angle still shows evidence of a bartizan, whilst substantial corbels on the western face suggest a now-demolished adjoining building, possibly a seventeenth-century house. Interestingly, the castle stands just 35 metres south of an even earlier fortification; a twelfth-century Anglo-Norman motte castle, reminding visitors that this corner of Thurles has been strategically important for nearly a millennium. Today, surrounded by modern buildings and a car park, the Black Castle continues to dominate its urban setting, a tangible link to the powerful Butler dynasty that once controlled much of medieval Tipperary.