That small asymmetry caught the attention of antiquarian Hubert Knox when he visited in 1911, and he proposed that the stones might mark the mouth of a souterrain, an underground passage of the kind that early medieval ringfort builders sometimes dug beneath their enclosures for storage or refuge. Whether he was right remains unverified, but the boulders give the site an air of quiet deliberateness, as if something was once meant to be found, or hidden, at that exact spot.

The earthwork itself is a rath, a type of circular enclosure built during the early medieval period, typically between the fifth and twelfth centuries, and used as a farmstead by a single family or small household. This one sits on a low knoll along a northeast to southwest ridge in Levallyroe, overlooking Levally Lough some 80 metres to the south-east. A meandering river runs about 180 metres to the north-east, and both the 1838 and 1916 Ordnance Survey six-inch maps show a corn mill at that location, suggesting the surrounding landscape was actively worked long after the rath fell out of use. The circular platform measures roughly 33 metres across and is defined by an earthen inner bank, a fosse (a wide ditch, here between 3.4 and 4.3 metres across), and an external bank beyond that. The name Knox recorded in 1911 was Doonooir; the form Doonfore Fort only appears on the 1988 Ordnance Survey map. Off the western entrance, the bank widens noticeably at its southern terminal, and a rectangular area beyond it, roughly 15 by 20 metres, was interpreted by Knox as an annex attached to the rath. He noted even then that its outline was faint, and it is largely invisible now beneath gorse and brambles.

The site sits in rough pasture and the rath itself is covered in long grass, with scrub encroaching around its edges. A quarry pit roughly 18 metres across cuts into the southern part of the fosse and external bank, and the outer bank on the west and northwest has largely disappeared. Two hundred metres to the north-west, a low hill holds what may be a second rath, its relationship to Doonfore unexamined.