A cashel is a type of early medieval stone ringfort, typically enclosing a farmstead or small settlement, and this one contains what may be a souterrain: an underground stone-lined passage or chamber that served as storage space, refuge, or both. The evidence is subtle but legible to a trained eye, a protruding stone in the interior that resembles a lintel, the kind of capstone that would have roofed a subterranean corridor, and a narrow depression running north to south, roughly six and a half metres long and one and a half metres wide, with traces of what appear to be side-walls still visible along its edges.

The site was noted by McCaffrey in 1952, who recorded it among a catalogue of similar features in the region. The conditional language around it matters: this is a possible souterrain rather than a confirmed one, which places it in a genuinely interesting category of archaeology, sites where the ground has not yet been opened, and where the interpretation rests on surface reading alone. Souterrains are found across Ireland in association with early medieval settlements, and their purposes were likely varied, keeping dairy produce cool, sheltering livestock or people during raids, or simply providing dry underground storage in a wet climate. Here at Ballywinna, the cashel itself provides the broader context, and the souterrain, if that is what it is, would have been a functional feature of whatever community once lived within those walls.