A sunken area ringed by a low, semicircular mound marks the presence of something beneath the surface, a souterrain lying undisturbed below the field. Souterrains are underground stone-lined passages or chambers, built during the early medieval period and associated with ringforts across Ireland. Their exact purpose is still debated, but they are generally thought to have served as places of refuge, storage for perishables, or both, taking advantage of the stable cool temperature underground.

The ringfort at Lisselane, recorded as CO122-086001, is the structure within which this souterrain sits. Ringforts, also known as raths, were enclosed farmsteads typically dating from roughly the sixth to the tenth centuries, defined by one or more earthen banks and ditches. The souterrain here has not been excavated or formally opened; what survives above ground is simply the slight depression and its surrounding mound, the earth having settled over centuries into the shape of whatever chamber or passage lies below. That subsidence is, in its quiet way, the whole story, a surface record of something deliberately hidden.