A tunnel that goes nowhere and was found alongside two ogham stones, inside a ringfort that no longer exists, is something else entirely. This is what was discovered at Dunbell Big in County Kilkenny during mid-nineteenth-century excavations, and the site has since been quarried out of existence, leaving only the written record of what was once there.

A souterrain is an underground stone-lined passage, typically associated with early medieval ringforts and used for storage, shelter, or refuge. The one uncovered at Dunbell Big defied easy categorisation from the moment it was found. Writing in the 1850s, the antiquarian J. G. A. Prim described opening an aperture on the north-east side of a ringfort's inner embankment, its entrance formed by three flat stones, two upright and one laid across the top, measuring two feet four inches high and one foot eight inches wide. It had the immediate appearance of a creep, the narrow crawl-through entrance common to souterrains, but the passage narrowed so sharply that no person could advance more than three or four feet. When fully excavated, it measured just thirteen feet six inches in total length and ended without opening into any chamber. It ran parallel to the embankment and had no vent, ruling out any drainage function. Prim was candid about his puzzlement, offering no firm conclusion as to its purpose. Near the entrance, to the north-north-east, excavators also found two ogham stones, the inscribed standing stones associated with early medieval Ireland in which an alphabet of notches and scores along a central line encodes names, most often those of individuals. What connection, if any, those stones had to the souterrain was not established.

Prim noted in his own annotated map, produced in the 1870s, that the ringfort in question was by then nearly obliterated. It has since been completely quarried away, taking with it whatever remaining context might have helped explain a passage that, in its brief and baffling dimensions, prompted more questions than it answered.