What once lay beneath the surface was a souterrain, a type of man-made underground passage or chamber built from unmortered stone, commonly found across Ireland in association with early settlement sites and used variously for storage, refuge, or both.

When archaeologists first examined the site in March 1983, the structure consisted of a single drystone-built chamber running northwest to southeast, measuring 4.6 metres in length and 1.6 metres in width. Entry was through an opening at the southeast end. The northwest end had partially collapsed, but beyond the rubble, surviving roof lintels hinted at something more complex, possibly a creep, which is a low, deliberately narrowed passage connecting one chamber to another, and perhaps a second chamber altogether. That tentative promise of further extent went uninvestigated. At some point after the initial visit, the chamber was filled in as part of land reclamation work, and today no visible trace of it remains on the surface.

The site is now, in a practical sense, gone. What makes it worth noting is precisely that finality. The lintels suggesting a second chamber, the possible creep passage, the full extent of the underground arrangement, none of it was ever fully recorded or excavated before the ground closed over it. McCaffrey had noted the location as far back as 1952, decades before the structure was formally examined and then lost entirely.