That uncertainty is, in its own quiet way, the whole story. A souterrain is an underground passage or chamber, typically built during the early medieval period, used variously for storage, refuge, or purposes that archaeologists still debate. They are found across Ireland in their hundreds, often tucked beneath ringforts or cashels, and usually detectable by slight depressions in the ground or telltale arrangements of stone. At Bolisheen, when an inspection was carried out in 1990, none of that was visible. The surface gave nothing away.

What prompted the investigation in the first place was local knowledge, the kind that gets passed down without being written down. Someone, or several someones, knew the site as a place with a cave inside the cashel, a cashel being a ringfort enclosed by a stone wall rather than an earthen bank. That oral record was enough to flag the site, but the ground itself refused to confirm it. Whether the souterrain has collapsed and settled into invisibility over the centuries, or whether it survives intact below the surface simply waiting, is a question the 1990 inspection left open.