It has been identified as the seat of the Kingdom of Ailech and one of the royal sites of Gaelic Ireland. The monument clearly has ancient origins and surrounding the stone fort are the remains of a much older hill fort that was most likely constructed around 1000BC. There is also a small stone cairn nearby that is most likely a burial monument from the Neolithic or Early Bronze Age.
The stone fort is believed to have been constructed during the 8th or 9th century as the seat of Cenél nEógain, rulers of the ancient kingdom of Aileach. The interior of the circular fort measures some 23m across and an entrance passage extends through the thickness of the massive encircling wall. This dry-stone wall stands some 5m high and incorporates a series of terraces that are accessed by stone steps.
The current hill fort, after the restoration of 1874–1878, is substantially different but much of the old structure remains intact. During the restoration, it was found that parts of the original dry stone masonry had been preserved under the collapse. The workers used the collapsed stone to build on this foundation. They supplemented these with other stones from the area to replace those removed by King Murdoch O’Brien in 1101.