The Grianan of Aileach (Irish: Grianán Ailigh, sometimes anglicised as Greenan Ely or Greenan Fort) is a group of historic structures atop a 244 metres (801 ft) hill in Inishowen in County Donegal, Ireland. The main structure is a stone ringfort, This great Cathair is said to have been originally built by the Daghda, the celebrated king of the Tuatha De Danann, who planned and fought the battle of the second or northern Magh Tuireadh, against the Fomorians. The fort was erected around the grave of his son Aedh, (or Hugh), who had been killed through jealousy by Corrgenn, a Connacht chieftain. The history of the death of Aedh, and the building of Aileach, is given at length in a poem preserved in the Book of Lecan which has been printed with an English translation (verse 38 Ordnance Memoir