The site at Rubble reveals stone foundations and partial walls that once formed part of a medieval stronghold, likely built during the Anglo-Norman period when such fortifications dotted the western Irish landscape. Though time and weather have reduced the structure to its current state, the remaining masonry offers valuable insights into medieval construction techniques, with its thick limestone walls and defensive positioning overlooking the surrounding terrain.

Archaeological evidence suggests the castle may have belonged to one of the prominent Gaelic or Anglo-Norman families who controlled this region during the turbulent medieval period. The strategic location would have allowed its inhabitants to monitor trade routes and defend against raids, a constant threat in an era marked by shifting alliances and territorial disputes. Local tradition holds various theories about the castle's demise; some attribute its destruction to Cromwell's forces during their campaign through Connacht in the 1650s, whilst others suggest it was deliberately slighted much earlier during inter-clan warfare.

Today, the ruins serve as both a historical landmark and a reminder of Mayo's complex past. The site remains largely unexcavated, meaning potentially significant archaeological discoveries may still lie beneath the rubble and overgrowth. Visitors can freely explore the remains, though care should be taken as the stonework is unstable in places. The castle ruins, whilst not as grand as some of Ireland's more famous fortifications, provide an authentic glimpse into the network of smaller defensive structures that once formed the backbone of medieval Irish society.