Originally known as Lough Gur Castle or Castle Doon, this five storey fortress belonged to the Earls of Desmond until the Bourchier family claimed it in 1588. The castle’s strategic position on what was once an island is remarkable; it sits on a narrow causeway with Lough Gur stretching 190 metres to the north and a smaller lough 155 metres to the south. Thomas Dineley’s 1680 drawing reveals that Knockadoon was then completely surrounded by water, accessible only via a long bridge defended by drawbridges, with the castle complex including a two storey house, barns, stables, and a pigeon house that still stands nearby.

The tower house itself is a fine example of sectional construction, a building technique where different portions were erected in phases but cleverly bonded together. Measuring approximately 15 metres by 10 metres and rising to nearly 23 metres high, the rectangular structure was built in two main sections. The eastern third, containing the entrance lobby and spiral staircase, was constructed first with its own corner quoin stones, whilst the larger western section housing the main chambers was tied in during a second phase using projecting through stones. The pointed doorway in the east wall leads into a defended lobby area, complete with an overhead murder hole, a guard room in the southeast corner fitted with circular gun ports, and access to the spiral stairs in the northeast angle. Each of the five storeys features vaulted ceilings, with the upper floors displaying elegant ogee headed windows with hood mouldings, including a particularly fine four light mullioned and transomed example from the 16th century.

Historical accounts paint a vivid picture of the castle’s importance and grandeur. In 1536, Crown forces described it as James of Desmond’s chief fortress in County Limerick, praising its natural defences of water, mountains and rocks. By 1583, a detailed survey recorded nine separate rooms, a barbican with a defensive turret, and grounds that included an island, orchard, garden and various cottages for tenants. Dineley noted that the surrounding waters teemed with pike, eels and especially roach, whilst inside the castle hung an armorial plaque of the Bourchier family, featuring their coat of arms; argent a cross engrailed gules between four water bougets sable, marking their connection to John Bourchier, Earl of Bath. Today, though the interior remains inaccessible to visitors, the castle’s exterior continues to showcase the sophisticated defensive architecture and construction techniques of late medieval Ireland.