It extends just 0.9 metres before hitting a blockage, yet its presence within one of Kerry's better-preserved early medieval settlements is enough to raise questions that no one has fully answered. Whether it was ever a functioning souterrain, which is a stone-lined underground passage typically used for storage, refuge, or ventilation in early Irish settlements, or simply an abandoned construction effort, remains uncertain.

The site itself, known in Irish as Cathair Deargáin, is a roughly circular cashel, a type of dry-stone enclosure characteristic of early medieval Ireland, set on a west-northwest facing slope with wide views across the northern side of the Dingle Peninsula. Inside the enclosure stand five well-preserved clocháns, the corbelled dry-stone huts associated with early Christian and pre-Christian habitation in this part of Munster. The possible souterrain passage is partly built into the fabric of the wall of one of these huts, and opens onto the ground just outside the structure to the north. The 1986 Dingle Peninsula archaeological survey by J. Cuppage, which remains a foundational reference for this area, recorded it with careful hedging, noting one or possibly two souterrains at the site, which suggests the evidence on the ground was ambiguous even then.

The truncated passage is easy to overlook in a site that already offers five intact clocháns and a substantial cashel wall, but it is precisely its incompleteness that makes it worth pausing over. A souterrain that runs less than a metre before stopping tells you something about interrupted plans, collapsed sections, or construction that was never finished, though which of these applies here is not recorded.