A souterrain is an underground stone-built passage or chamber, typically constructed during the early medieval period and associated with nearby settlement sites, most likely used for storage or refuge. This one has left no mark on the ground above it, no depression, no exposed stonework, nothing a casual observer would notice or pause over.

What makes it possible to locate at all, at least on paper, is a combination of two things. It sat within the interior of a cashel, a type of early medieval stone-walled enclosure that would once have defined a farmstead or small settlement, and that cashel is itself a recorded site. More intriguingly, the 1933 edition of the Ordnance Survey six-inch map labelled this feature simply as "Cave", a word that suggests whoever named it either encountered an opening of some kind or was working from local knowledge that has since dissolved entirely into the landscape. By the time any formal record was made, no visible surface trace survived.