A souterrain is an underground stone-lined passage or chamber, typically built during the early medieval period and associated with nearby ringforts or settlements; they were used variously for storage, refuge, or concealment. What makes this particular example quietly striking is how little is known about it beyond the bare fact of its existence.

Around 1970, local activity of some kind brought the souterrain to light. No excavation report followed, no dimensions were recorded, and no details of construction or associated finds were preserved in any formal way. The discovery passed into local memory and then, to a large extent, out of it. By the time it was noted in the archaeological record, the information amounted to little more than an approximate date and a placename. The ground above has since closed back over it, leaving no visible surface trace.

There is genuinely nothing to see at this site, and that is rather the point. It serves as a reminder that the Irish countryside holds a considerable number of archaeological features that were noticed once, briefly, and never properly documented. Knockshanawee keeps its souterrain to itself.