Grianan of Aileach

The Grianan of Aileach (, sometimes anglicised Greenan Ely) is a group of historic structures atop a hill in County Donegal, Ireland. The main structure is a stone ringfort, thought to have been built by the Uí Néill in the sixth or seventh century CE; although there is evidence that the site had been in use before the fort was built. It has been identified as the seat of the Kingdom of Ailech and one of the royal sites of Gaelic Ireland. The wall is about thick and high. It has three terraces, which are linked by steps, and two long passages within it. Originally, there would have been buildings inside the ringfort. Just outside it are the remains of a well and a tumulus.