Grianan of Aileach (Irish: An Grianán an Aileach \ An Grianán Ailigh) are the ruins of an Iron Age stone fortress in County Donegal in the north-west of Ireland which was the seat of the Kingdom of Aileach (Aileach). The kingdoms of Ulaidh and Airgiallaigh were two subject kingdoms in the North under the general rule of Aileach, making this fortress a historical centre of culture and politics during the rule of early Irish chieftains (c. 800 B.C.E.-1200 C.E.). An Irish creation myth claims that this fortress was built by the great king Daghda of Tuatha de Danann. The grave of the king's son Aeah was in the centre of the fortress, which had been built around it. By the 12th century, the Kingdom of Aileach had become embattled and lost a fair amount of territory to the invading Normans. By around 1177, the Normans controlled large portions of lands once held by Aileach. The fortress of Grianan of Aileach therefore over time ceased to hold as much importance as a regional centre a
