The first edition Ordnance Survey six-inch map of 1841 marks a feature labelled 'cave' just outside the enclosing bank of a nearby ringfort. Later editions of the same map omit it entirely, as though whoever revised the survey thought better of including it, or simply could not find it.

The feature is believed to be a souterrain, an underground stone-lined passage or chamber typically associated with early medieval ringforts in Ireland. Souterrains were built for a variety of purposes, most likely for food storage, refuge, or both, and they are commonly found either within or immediately adjacent to the enclosing banks of ringforts. The positioning of this one, just outside the eastern bank of the Tullig ringfort, fits that general pattern well enough to take seriously. When a site inspection was carried out in 1985, however, no visible trace of it remained at the surface. The pasture had either absorbed or concealed whatever might once have been detectable, and the inspection could confirm nothing definitive about what lay beneath.