There is nothing on the surface to suggest it is there. The ringfort it once belonged to has been levelled, the earthen banks that would have enclosed a settlement long since flattened, and the souterrain itself leaves no visible trace above ground. It is, in the most literal sense, a place that has disappeared.

The earliest known reference to it comes from a 1937 note by a researcher named Broker, who recorded it simply as an "underground chamber". That brief phrase is almost all that survives. The structure sits within, or rather beneath, the footprint of a ringfort, the circular enclosed settlements that were the dominant form of rural habitation in early medieval Ireland. Tens of thousands of ringforts once dotted the Irish landscape, and many were accompanied by souterrains, stone-lined tunnels whose precise purposes are still debated but which likely served as cool storage for dairy produce and as places of concealment in times of danger. At Knocknakilla, both the fort and its underground companion have been absorbed into the land, leaving only the archival record of their existence.