The site is not marked on any Ordnance Survey map, and the spot itself is now identified mainly by a patch of dense overgrowth, the kind of dense tangle that often signals disturbed ground or a collapsed void beneath.

The structure is a souterrain, a type of underground passage or chamber built from dry stone and roofed with large flat slabs, commonly found across early medieval Ireland and associated with nearby settlement sites. They were used variously for storage, refuge, or as concealed escape routes. The one at Rossacoosane reportedly consisted of three such stone-built chambers, according to local knowledge passed down over generations. A depression roughly 4.1 metres long, running north to south, likely marks the line of a chamber or connecting passage. One lintel stone, measuring 1.7 metres in length, still lies in place at one end of this depression. Other lintels were removed in more recent times, which has contributed to the collapse that now makes the interior inaccessible. The survey of the Iveragh Peninsula compiled by A. O'Sullivan and J. Sheehan, published by Cork University Press in 1996, recorded the site in this condition, noting the local oral tradition about the three chambers as the only surviving account of what the interior once looked like.