The evidence amounts to a slight depression in the ground and a hollow sound underfoot, noted by an investigator whose initials, PJH, are the only record of their visit. No stonework is visible, no entrance has been identified, and the ground gives nothing away beyond that faint acoustic suggestion of empty space below.

A souterrain is an underground passage or chamber, typically stone-lined, built during the early medieval period as a place of refuge or cool storage, and often associated with ringforts, the circular enclosures that dot the Irish countryside in their thousands. The ringfort here at Coolkisha is the context for this particular puzzle. What makes the site linger in the mind is the paper trail, thin as it is. The Name Books compiled during the Ordnance Survey of 1844 record a cave in one of the local forts, a detail noted in passing and not followed up with any excavation or formal investigation. The reference is brief enough that it is impossible to be certain it describes this precise location rather than a neighbouring fort, also known from the area. Over a century and a half later, the hollow sound and the depression are the only physical corroboration anyone has managed to offer.