Man-made underground passage in Rinn (oranmore Ed)

That is the largest chamber recorded in the county, a collapsed drystone vault seven metres long and two and a half metres wide beneath the northern half of a rath in Rinn. Someone cut through solid ground, fitted heavy stone across the span, and sealed the entrance, perhaps to keep heat, water or unwanted visitors out. The roof has fallen, but the chamber still stands as proof that the site was built for deliberate human use rather than left as an open mound.