A rath, or ringfort, is a roughly circular enclosure defined by an earthen bank and ditch, typically built during the early medieval period as a farmstead for a single family or small household. At Killunagher, the form survives only partially, and that partial survival is itself part of the interest. The western half of the enclosure retains a low, sod-covered stony bank, measuring roughly 3.5 metres wide with an external height of about 0.7 metres at the southwest. The eastern half has been levelled almost entirely, its outline dissolving into a slight undulation that the eye can just about follow before it merges with the natural lie of the land.

The site sits on elevated ground in gently undulating terrain, with the land falling away to the north and northeast toward an expanse of low-lying pasture and bog, a typical siting choice for raths, which were often placed to command a view of surrounding farmland. What makes the Killunagher example quietly telling is the record of its gradual erasure. The 1838 Ordnance Survey six-inch map shows a cluster of vernacular buildings and associated subrectangular field plots on the same ground, suggesting the area was still in active domestic use at that time, with no clear indication of the older structure beneath. By the 1916 edition, that earlier scene had disappeared, replaced only by a shallow hachured arc curving from south to northwest, already partially absorbed into a field boundary. The bank on the western side was very likely modified at some point to serve exactly that purpose, its ancient fabric quietly pressed into agricultural service. A second possible enclosure lies approximately 100 metres to the southeast, hinting that this corner of Mayo may once have held a small cluster of such settlements.