That ambiguity is precisely what makes the site interesting. The hollows are interconnected, spread across an area of roughly ten to eleven metres north to south and five metres east to west, and partly obscured by overgrowth. Stones protrude from the edges of some of them. Nobody has yet been able to say with certainty whether these are the collapsed remnants of a souterrain or simply the scars of later quarrying and disturbance.

A souterrain is a man-made underground structure, typically stone-lined and roofed with large flat slabs, built during the early medieval period in Ireland. They are commonly found inside ringforts, the circular enclosed settlements that were the dominant form of rural habitation from roughly the sixth to the twelfth century. Their purpose is debated; storage, refuge, and ventilation have all been proposed. The ringfort at Carrowcanada, a cashel built from stone rather than earthen banks, provides exactly the kind of context in which a souterrain might be expected. The largest of the hollows runs linearly for about ten metres, extending southward from close to the inner edge of the northern wall. Smaller subcircular depressions sit to the south and east of it. The pattern is suggestive, but the overgrowth and the degree of collapse make a definitive reading impossible from the surface alone.