It was uncovered accidentally by a mechanical digger, briefly exposed to daylight for what was likely the first time in well over a thousand years, and then backfilled. No marker was left. No surface feature remains. The ground looks, to all appearances, entirely ordinary.

What the digger found was a souterrain, an underground stone-lined passage or chamber constructed during the early medieval period, typically between the sixth and twelfth centuries. These structures were built by hand, cut into the earth and roofed with large flat stone lintels laid across the walls. Their precise function is still debated, though most archaeologists regard them as places of refuge, cool storage, or both, associated with nearby settlement sites that have often since vanished. The Teernahillane example, as described from local information, consisted of a single earth-cut chamber with a stone-lintel roof, which places it within the more modest end of the souterrain tradition. Some souterrains run to multiple interconnected chambers with carefully corbelled passages; this one appears to have been simpler, possibly serving a single farmstead or small community on the sheltered southern face of the mountain.

There is nothing to find at the surface now. The site sits in rough grazing land, unremarkable to the eye, and the chamber below has been covered over again. Its existence is known only because someone was present when the ground gave way, and thought to record what they saw.