This rectangular limestone structure, measuring approximately 11.3 by 15.7 metres, represents centuries of Prendergast family power in South Tipperary. From the 13th to the 17th century, the Prendergasts controlled the manor of Newcastle, with the Civil Survey of 1654-6 recording Edmund Prendergast, an ‘Irish Papist’, as the proprietor in 1640. The survey notes that the manor included court-leet and court-baron privileges, alongside ‘the walls of a house and a castle with a bawne about them and an orchard’.

Today, only the ground floor level of the tower house survives, topped by its original vaulted roof. The main entrance, positioned midway along the northeast wall, features an externally rebated and chamfered doorway with a yett-hole in its eastern jamb; a defensive feature that allowed a heavy wooden bar to secure the door. Within the 2-metre thick walls, a narrow mural staircase, just over half a metre wide, winds upward from the entrance. The interior consists of two barrel-vaulted chambers running northwest to southeast, connected by a central doorway in a partition wall that wasn’t keyed into the main structure, suggesting it may have been a later addition.

The northeast chamber, measuring 3 by 11.2 metres, received natural light through a flat-headed single window set in a deep splayed embrasure in the northeast wall, with another window, now blocked, in the southeast wall. The southwest chamber was similarly lit by a single window at the western end of the southwest wall. Later modifications are evident in this chamber, where the southeast wall has been broken out and replaced with a sandstone arch bearing a carved keystone dated 1796; its jambs rebuilt with concrete in more recent times. A garderobe chute, exiting about 1.3 metres above ground level at the northern end of the northwest wall, provided the medieval equivalent of indoor plumbing. The tower house’s high base-batter, rising 2 metres with a width of 0.12 metres, would have helped deflect projectiles whilst adding structural stability to this once-formidable fortress.