A shallow, square hollow measuring roughly 1.2 metres across and filled with loose stone is the only ground-level indication that a souterrain once existed here. A souterrain is an underground passage or chamber, typically dry-laid from stone, built in early medieval Ireland and often associated with the ringforts, or raths, that dot the Irish countryside. They served various purposes: cool storage for food, possible refuge, or concealed escape routes. At Grange More, even that modest hollow is uncertain as evidence; beyond it, no visible surface trace survives at all.

The rath itself, recorded separately, provides the broader context. Raths were enclosed farmsteads, usually defined by an earthen bank and ditch, and were the most common form of rural settlement in early medieval Ireland, built and occupied roughly between the fifth and twelfth centuries. The souterrain recorded at Grange More would have sat within or immediately beneath that enclosure, its entrance long since collapsed or deliberately blocked, its interior inaccessible. What remains is a slight depression in the ground, stone-choked and ambiguous, sitting inside the southern sector of the enclosing earthwork.