The site at Cornahoe is the kind of place that exists more fully on paper than on the ground, its clearest portrait being the 1834 edition of the Ordnance Survey six-inch map, where a circular embanked enclosure of roughly thirty-five metres in external diameter is marked in gothic lettering as a fort, the cartographers' shorthand for a ringfort.

Ringforts, known in Irish as ráth or lios depending on their construction, are among the most common early medieval monument types in Ireland, typically enclosing a domestic settlement within an earthen bank and ditch. Most date to somewhere between the sixth and tenth centuries, though many were in use before and after that span. The Cornahoe example, by the time anyone looked at it systematically, was already fragmentary. In 1984, traces of an earthen bank survived on the eastern, southern, and north-western arc of the enclosure, reaching a maximum height of about 0.7 metres at the east, with a diameter of approximately thirty-two metres east to west. Even then, the northern portion of the monument had been absorbed into a field boundary running east to west, and whatever archaeological feature may once have existed north of that line was no longer legible. By 1995, the field bank itself had been removed, taking with it any lingering trace of that northern arc.

What remains is a site defined largely by its absences, a monument that the 1834 map caught at the last moment of its relative legibility, and which has continued to diminish since. The ridge setting is characteristic, ringforts were often placed on elevated ground with good visibility across the surrounding landscape, and Cornahoe fits that pattern even if the enclosure itself is now more of an outline than a presence.