Today, we find ourselves in County Donegal in the northwest of Ireland. Grianan of Aileach, a stone ringfort—dating from the Iron Age to the early Middle Ages—linked to the Kings of Aileach and the Northern Uí Néill, stands here. The fort crowns Greenan Mountain and served as a ceremonial and strategic stronghold. Archaeological evidence suggests the site had importance long before the current walls rose in the 6th or 7th century.

The ring-shaped structure was built using tightly fitted stones without mortar, forming a strong circular enclosure with inner stairways and wall passages. Historical records state that the fort was destroyed in 1101 by Muirchertach Ua Briain during regional power struggles. By the 1800s the structure had collapsed into a stony mound, until restoration work in the 1870s rebuilt much of the fort using remaining material. From its hilltop position, the site overlooks Lough Foyle and Lough Swilly, giving visibility across lands.