It reaches no more than 0.75 metres in height, and only the western to northern section of the original circuit survives, but that modest bank is the remnant of a ringfort, a class of enclosed farmstead built predominantly during the early medieval period in Ireland. Locally, the site is known simply as "the lios", an Irish word for an enclosure of this kind, and the name has persisted in the area long after the structure itself faded into the field.

Ringforts are among the most common archaeological monuments in Ireland, yet each one carries its own particulars. This example sits on a slope rather than commanding high ground, which is not unusual but does suggest the site was chosen with an eye to drainage and shelter rather than visibility. Perhaps more intriguing is the record of a possible souterrain in the interior. A souterrain is an underground stone-lined passage or chamber, typically associated with early medieval settlement sites and thought to have served for storage, refuge, or both. Whether the one at Rahoonagh is intact, partially collapsed, or simply inferred from a surface depression is not entirely clear, but its presence would place this unassuming field feature in a broader pattern of domestic and defensive life stretching back well over a thousand years.