A souterrain, which is an underground stone-lined passage or chamber typically associated with early medieval ringforts and used for storage or refuge, once ran beneath a circular earthen enclosure here. It was built of drystone walling, dry-laid stone without mortar, a method that could produce remarkably stable underground structures. Both the fort above and the passage below were completely levelled, and the reason recorded is arrestingly mundane: a horse died inside the fort, and the decision was made to fill the whole thing in.

The enclosure had been documented on Ordnance Survey maps from 1841 to 1842 and again on the 1898 revision, and it was still visible enough to show up clearly on aerial photographs taken by the Geological Survey of Ireland in 1977. The souterrain's existence came to light not through formal excavation but through the account of the landowner, who described its construction before the levelling took place. That sequence, aerial photograph, landowner testimony, then obliteration, gives this site a particular quality. It passed through the documentary record just long enough to be counted, then was gone. The information was gathered as part of C. Toal's North Kerry Archaeological Survey, published in 1995, which captured details of many such sites across the region, some intact, some already lost.