It is roughly thirty metres across, its defining bank of earth and stone worn down to the point where it barely asserts itself above the surrounding grassland. Yet this modest ring, a rath of the kind built in early medieval Ireland as a farmstead enclosure for a family of some local standing, carries within its northern interior something that lifts it slightly above the ordinary: traces of what may be a souterrain.

A souterrain is an underground passage or chamber, typically constructed from stone, and associated in Ireland with the early medieval period, roughly the fifth to twelfth centuries. They are found beneath many raths and were used variously for storage, refuge, or ventilation of perishable goods. The one at Rafarn is tentative, recorded as a possibility rather than a confirmed feature, but its presence in the northern sector of the interior is enough to suggest that what survives above ground is only part of a more complex original arrangement. The rath itself, circular and defined by a single earthen bank, fits the most common type of ringfort found across the Irish countryside, thousands of which were constructed across the island during the early medieval period as the basic unit of rural settlement.