What emerged was a souterrain, the term for a type of stone-lined underground structure found widely across early medieval Ireland, typically associated with nearby settlement and used variously for storage, refuge, or concealment. This one is modest in scale but precise in its construction, two chambers meeting at right angles, connected by a low creepway just long enough to make the passage between them awkward.

Following the discovery, Martin Byrne and Louise Lynch of University College Cork investigated the site and recorded its layout in some detail. The first chamber runs north to south, stretching 3.5 metres in length but only 0.96 metres wide, with a height that varies between 0.8 and 1.25 metres, meaning anyone inside would need to stoop or crouch. Its side walls lean inward toward the top, a corbelling technique that helps distribute the weight of the earth above. Three lintels remain in place at the northern end, where the ground rises toward the surface and the original entrance is thought to have been. A short creepway, just 1.2 metres long and roofed with five lintels, connects this chamber to the second. That second chamber runs east to west, is slightly shorter at 2.65 metres, and enters from the midpoint of the first chamber's northern wall. It is more regular in shape, roughly rectangular with gently rounded corners, and stands a little taller at 1.45 metres, with three lintels still in place at its western end. The whole structure has the quality of something built by people who knew exactly what they were doing and why, even if the precise reason has not survived with it.