The absence itself is the point. A souterrain, to give the feature its proper name, is a man-made underground structure, typically constructed from drystone walling and roofed with large capstones, and associated in Ireland with the early medieval period. They are found beneath and alongside ringforts throughout the country, and were likely used for storage, refuge, or both. That this one has no visible surface trace means it survives, if it survives at all, as a buried feature entirely, known only through local memory rather than any mark on the ground.

The souterrain sits within, or is associated with, a ringfort at Rushfield, a type of enclosed settlement that was the dominant form of farmstead in early medieval Ireland, typically defined by one or more earthen banks and ditches encircling a domestic area. The ringfort here carries its own separate record. Local information, rather than direct excavation or survey, is the source for the souterrain's existence, which places it in a category of sites that archaeology acknowledges but cannot fully verify without ground investigation. That tentative status, known to the community but invisible to the eye, gives the site an unusual character even among underground monuments.