Dun Aengus is the most visited of the four stone forts on Inis Mor , it is located close to the village of Kilmurvey. The fort consists of three terraced walls, five metres high and four metres thick, surrounding an inner enclosure containing a platform on the edge of a one hundred metre high cliff. Surrounding the walls is a remarkable network of defensive stones known as a Chevaux de Frise. Archaeological reports suggest that the fort was once inhabited, though scholars have also suggested that as the platform faces out over the Atlantic it could have been used for ritual purposes. It is thought that parts of the cliff have collapsed into the sea. 

The views from Dun Aengus are absolutely spectacular. It is about a twenty minute walk from the small museum just off the main road. There isn't a proper footpath so care should be taken, especially when it's raining as it can become quite slippy. Be aware that there is no railing at the edge of the cliff so if you visit with young children take extra care. Checkout the Dun Aonghasa website.