Built in the early 17th century by the Bourke family, this fortified house represents a transitional period in Irish architecture when the traditional tower houses of medieval times were giving way to more comfortable, yet still defensible, residences. The castle’s distinctive features include its rectangular plan, thick limestone walls, and narrow window openings that once served both defensive and domestic purposes.

The Bourkes, who constructed Denne Castle around 1620, were part of the Norman-Irish aristocracy that had established themselves in Connacht following the Anglo-Norman invasion centuries earlier. The castle served as their stronghold during a turbulent period of Irish history, witnessing the Confederate Wars of the 1640s and the subsequent Cromwellian conquest. Local tradition holds that the castle was attacked and partially destroyed during Cromwell’s campaign through Mayo in 1652, though it continued to be inhabited intermittently until the 18th century.

Today, the castle ruins offer visitors a glimpse into the complex layers of Mayo’s past. The structure retains much of its original footprint, with sections of the main hall, spiral staircase, and defensive features still visible despite centuries of neglect. Archaeological surveys have revealed evidence of earlier settlements on the site, suggesting that this strategic location overlooking the River Deel has been significant to local communities for far longer than the castle itself has stood. The surrounding landscape, dotted with ringforts and other archaeological features, tells a broader story of continuous habitation stretching back to prehistoric times.