The rath at Carrowleagh sits on a south-west-facing slope, a position that would once have offered its inhabitants a practical combination of shelter, drainage, and a long view across the surrounding bogland and rough pasture. Today the forestry plantation that has grown up around it makes the site almost inaccessible, and dense overgrowth had already impeded any close inspection when the site was recorded.

A rath is a ringfort, the most common type of early medieval settlement in Ireland, typically consisting of a raised circular or oval enclosure bounded by one or more earthen banks and ditches. They were in general use between roughly the sixth and tenth centuries and served as enclosed farmsteads for families of some local standing. The Carrowleagh example follows the expected pattern: a broadly oval area of approximately 35 metres on its longer axis, defined by a low earthen bank that has largely slumped into a scarp no more than 0.45 metres high at its north-west point. Around that inner bank runs a fosse, a defensive ditch some 4.5 metres wide, and beyond that an outer bank still standing between 0.85 and 1 metre in height internally. The outer bank is the better-preserved element, which is often the case where the interior has been disturbed or where the ground has settled unevenly over centuries. A river runs roughly 50 metres to the south-east, close enough to have supplied the original occupants with fresh water and perhaps to have marked a boundary of the holding.