One sits near the centre of the enclosure, the other close to its southern bank, and between them they suggest something lies underneath: a souterrain, an underground passage or chamber built during the early medieval period, typically from stone, and used for storage, refuge, or both.

Ringforts, the circular earthen or stone enclosures that dot the Irish countryside in their thousands, were farmsteads of the early medieval period, roughly from the fifth to the twelfth century. Souterrains are frequently found within them, tunnelled beneath the living area and sometimes connecting to the interior of the enclosing bank. They were practical spaces, cool enough to preserve food and occasionally deep enough to shelter people in times of danger. At Kilkinnikin, nothing has been excavated or confirmed below ground, but the surface evidence is suggestive. Two distinct depressions of that kind, positioned as these are, are a recognised pattern. The ground has settled, or partially collapsed inward, where the underground structure has shifted over centuries.

The site sits within a wider landscape of West Cork that has retained a remarkable density of early medieval remains largely because so much of the land was never subject to intensive modern development. The ringfort itself is recorded, and the souterrain noted as implied rather than confirmed, which is its own kind of historical honesty: an absence of certainty held open rather than papered over.