Measuring just thirty inches across and only a few inches high, the opening leads into a souterrain, an underground stone-built passage or chamber constructed in early medieval Ireland, typically for storage, refuge, or both. Most souterrains were built to be entered; this one, by contrast, seems to have been doing its best to stay forgotten.

The site was noted by Hartnett in 1939, who recorded the narrow entrance and observed that, while the passage itself was inaccessible, the stone walling and roof lintels were visible from the opening. The souterrain sits within what may be an early ecclesiastical enclosure, the kind of roughly circular or oval boundary that often surrounded early Irish monastic or religious sites, though the ecclesiastical character of this particular enclosure has not been confirmed. That context, if genuine, would place the underground passage within a tradition of early Christian settlement in the Cork countryside, where such structures frequently appear in association with churches, ringforts, and farmsteads dating from roughly the sixth to the twelfth centuries.

The opening is still visible inside the northern bank of the enclosure, just to the west of the road. It has not grown more accessible with time. What can be seen is essentially what Hartnett saw: the mouth of something older than the road beside it, and the suggestion of a stone-lined interior that nobody has entered in a very long time.