Built around 1410 when Walter Duff Burk granted these lands to his third son Tiboit, the castle became the principal seat of the Bourkes, who would later become the Barons of Brittas. The surviving remnants include a striking circular tower at the southwest corner, rising some 40 feet high with walls five feet thick, connected by an 84-foot curtain wall that once formed part of this formidable defensive structure. Archaeological evidence suggests the castle may date back even earlier to the 13th century, with arrow loops featuring distinctive blank oillets and a dome vault within the tower.

The castle’s history is steeped in drama and defiance. Local legend claims that Frederick Bourke, the first Lord Brittas, murdered his own father-in-law, Mornane of Carrigarreely, whilst another tale tells of a northern chieftain who forced his way to “Boreen a Charrig” during the Elizabethan Wars, where he slew Lord Brittas and 21 other Bourkes. The most compelling story, however, belongs to Sir John Bourke, who in 1600 considered it “sinful and damnable” to personally submit to Queen Elizabeth I. After imprisonment for refusing the oath of supremacy in 1603, he held the castle against government forces for fifteen days before fleeing to Waterford, where he was captured and hanged. His kinsman Theobald was later created Baron of Brittas in the early 17th century, though the family’s fortunes would eventually decline following the Williamite Wars, with the last Lord Brittas fleeing to France in 1691.

Recent archaeological excavations in 2012 revealed that the castle site contains deep cultural layers dating from at least two distinct periods, with 17th and 18th century material overlying earlier medieval deposits rich with charcoal, animal bone and organic material. The Civil Survey of 1654-56 recorded “two castles and a bawen” at Brittas, though the location of the second castle remains a mystery. Today, whilst much of the structure has succumbed to time, what remains of Brittas Castle serves as a tangible link to centuries of Irish resistance, family feuds, and the complex political landscape of medieval and early modern Limerick.