It was found, covered over with a stone slab, and then effectively swallowed again by the landscape. No depression in the ground marks it, no signage points toward it, and nothing at the surface hints that anything lies below. It is, by all practical measures, invisible.

The tunnel is a souterrain, an underground passage or chamber built, typically during the early medieval period in Ireland, from dry-laid stone or cut into bedrock. Souterrains are found across the country and are generally associated with ringforts, the circular enclosed settlements that were the dominant farmstead type of early medieval Ireland. This one sits on the eastern side of just such a ringfort at Knockantota. The details of its discovery are thin: local information, a stone slab, and then silence. Whether it was explored in any depth before being left as it was is not recorded. What remains is the knowledge that it is there, somewhere underfoot, doing what souterrains have always done, which is persist quietly while the world above them gets on with things.