The record is unambiguous on this point: the structure lies in the north-eastern quadrant of a ringfort, and there is no visible surface trace. A souterrain is an underground passage or chamber, typically stone-lined, built during the early medieval period in Ireland, most commonly as a place of refuge or cool storage associated with a nearby settlement. Here, even the ringfort above it has left little for the casual eye to read in the landscape.

The pairing of souterrain and ringfort is thoroughly Irish. Ringforts, which are enclosed farmsteads of the early medieval centuries, were often equipped with these subterranean annexes, and many souterrains survive only because they happen to be recorded rather than visible. The Kilblaffer example sits within a ringfort catalogued in the Cork monuments record, and its existence is known from survey rather than from any feature you might trip over or photograph. That is not unusual in itself; a great many souterrains across Ireland were identified through accounts from local landowners, slight ground disturbances, or the collapse of a roof that revealed a void below. What is notable here is the completeness of its invisibility, a known thing that presents nothing of itself to the surface world.