What is known is that a section of natural rock outcrop protrudes into its interior, an unusual feature that suggests the builders worked around or incorporated the existing geology rather than clearing it away. Souterrains are underground stone-lined passages or chambers, typically constructed during the early medieval period in Ireland, and associated with settlement sites; they were used variously for storage, refuge, or as escape routes.

The detail about the rock outcrop comes from a 1996 archaeological survey of the Iveragh Peninsula compiled by A. O'Sullivan and J. Sheehan, a comprehensive study of a landscape that contains an exceptional concentration of early medieval and prehistoric remains. That the souterrain is described as "reputedly" located here, on the basis of local information, places it in an interesting category of sites: known to the community, acknowledged by researchers, but not yet fully documented or excavated. The Iveragh Peninsula, which forms the backbone of the Ring of Kerry, has long been recognised as archaeologically dense, and many of its monuments remain incompletely surveyed.