Grianan of Aileach

 Grianan of Aileach, an Iron Age stone fortress that was used from about 800 BC till about 1200 CE; located in County Donegal, Ireland.

According to legend, it was built by renowned King Daghda of Tuatha de Danann. Supposedly, king’s son Aeah was buried in center of fortress.

Fort was seat of Kingdom of Aileach, that ruled much of Ulster at that time. It was raised once by Vikings, and Murtaigh O’Brien, Kind of Munster finished job in 1191 CE. It was restored to its current state in 19th Century CE.