What it actually represents is something more deliberate and more ancient: a souterrain, one of the underground stone-lined passages built across early medieval Ireland, typically as storage spaces or places of refuge associated with nearby settlement. The OS label is an honest enough mistake; from the surface, the site presents itself as a trench rather than anything obviously architectural.

The trench runs for roughly eight metres, aligned on a northwest to southwest axis, and is thought to mark the dug-out section of the souterrain. It sits just to the southeast of a hut site, which places it in a pattern familiar from early Irish settlement archaeology, where souterrains were commonly dug close to, or even beneath, domestic structures. At the northeastern side of the trench, a short stretch of drystone masonry survives in good condition, the careful dry-laying of stone without mortar that characterises these constructions. This detail is significant: it is the kind of physical evidence that distinguishes a genuine souterrain from simple subsidence or a natural hollow. The site was documented by A. O'Sullivan and J. Sheehan in their 1996 archaeological survey of the Iveragh Peninsula, a comprehensive study of south Kerry's prehistoric and early historic remains published by Cork University Press.