A souterrain, an underground stone-lined passage typically associated with early medieval settlement and used for storage or refuge, once lay in the north-eastern quadrant of a rath, one of the circular earthen enclosures that served as farmsteads across Ireland during the early medieval period. The rath itself was already the kind of site that passes unremarked in the landscape, a grassy ring where cattle might graze and local people might vaguely sense that something old lay underfoot. The souterrain beneath it was even less visible, buried and essentially invisible until it was not there at all.

What we know of both features comes from the 1919 Ordnance Survey six-inch map, which marked the souterrain's position within the enclosure. At some point after that survey, the ridge on which the rath and its souterrain stood was quarried away entirely, removing both monuments from the ground. The quarrying left no trace of the earthwork or its underground chamber. It is a pattern that recurred across Ireland throughout the twentieth century, as agricultural improvement, road-making, and the extraction of stone and gravel consumed sites that had survived, largely by accident, for over a thousand years. Liscosker offers a particularly complete version of that loss: rath, souterrain, and the very landform that supported them are all gone.