This circular mound rises about six metres high with a flattened summit spanning 29 metres across. A defensive fosse, eight metres wide, encircles the entire structure, whilst an outer earthen bank adds another layer of fortification; its inner face stands 1.8 metres tall, with the outer reaching two metres. The southern approach features the original entrance, just 3.5 metres wide, where an ancient ramp still provides access up the side of the mound.

The summit holds an intriguing feature: an oval hollow approximately five metres long in its eastern half, suggesting the remains of some internal structure. When antiquarian Knox examined the site in 1911, he noted its striking resemblance to a Norman motte, an observation later supported by Glasscock’s 1975 catalogue of Irish mottes. The defensive design, with its steep sides, encircling ditch and elevated position, certainly fits the pattern of these early medieval fortifications that the Normans introduced to Ireland.

Most fascinating is the possibility that this earthwork marks the location of Ath-na-Gail castle, a fortress with a brief but dramatic history. According to historical records, MacWilliam Burke erected this castle in 1265, only for Aedh O’Connor to demolish it just five years later in 1270. If this identification proves correct, the mound at Rathdoony More represents a tangible link to the complex power struggles between Gaelic lords and Norman settlers that shaped medieval Connacht, frozen in earth and stone atop its windswept ridge.