These guidelines called for structures measuring 20 feet long, 16 feet wide and 40 feet high; dimensions that Donore closely follows at roughly 7.3 by 6.3 metres. The four storey tower, with its distinctive rounded corners and circular stair tower projecting from the southwest angle, once belonged to Garrat Lench of the Killaconnigan parish. According to the Civil Survey of 1654-6, Lench owned 220 acres here in 1640, complete with the castle, an orchard, a weir and several cottages, alongside substantial holdings throughout the parish totalling nearly 750 acres.

The castle’s interior tells the story of medieval defensive architecture through its carefully designed features. Entering through the western wall, protected overhead by a machicolation at parapet level, visitors would have passed through what was likely a murder hole controlled from the first floor ante-chamber; a grim reminder of the building’s defensive purpose. The ground floor retains only a double-splay window in its north wall, whilst the first floor sits beneath a barrel vault running north to south. Each ascending level reveals different architectural elements: narrow windows with built-in seats, a fireplace on the second floor’s western wall, and a garderobe chamber cleverly built into the thickness of the eastern wall. The original ceiling joists were supported by corbels set into the long walls, seven on each side at ground level, though these have since been removed.

By 1785, an illustration shows the castle still occupied and sporting a hip roof, suggesting it had successfully transitioned from medieval fortress to more comfortable dwelling. Though the parapet no longer survives and the stair tower has suffered considerable damage, the structure remains a National Monument (No. 232), offering valuable insights into how the Anglo-Norman settlers defended their holdings along the edges of the Pale. The possible gun-loop in the upper stairs section hints at later modifications, perhaps reflecting the changing nature of warfare as medieval times gave way to the early modern period.