Souterrains are underground stone-built passages and chambers, typically associated with early medieval settlement in Ireland, and thought to have served as places of refuge or storage. This one was found only because the ground beside it was being dug away commercially, which makes the discovery almost incidental, a side effect of industry rather than any deliberate archaeological enquiry.

According to local information gathered at the time, the structure consisted of two stone-built chambers connected by a creepway, the narrow linking passage characteristic of this type of monument, low and tight enough to slow an intruder considerably. Its location within a graveyard at Kilnacranagh suggests it may have been associated with an early ecclesiastical site, a common pairing in the Irish landscape, where souterrains sometimes lie close to early church enclosures. The discovery was not followed by any preservation effort. The souterrain was subsequently destroyed, leaving no physical trace for anyone to visit or study further.

What remains is essentially a footnote: a structure that existed for perhaps over a thousand years before being erased within a short window between its accidental discovery and the continuation of quarrying work. The graveyard at Kilnacranagh still marks the spot, but the underground chambers and their creepway are gone.