Stone steps lead down into a narrow tunnel, roughly a metre wide and a metre high, roofed with flat capstones laid lintel-fashion across the walls. A souterrain, to use the term common in Irish archaeology, is an artificial underground passage or chamber, typically associated with early medieval settlement, and used for storage, refuge, or both. This one, set among wooded ground with occasional outcrops of natural rock breaking the surface, is modest by any measure, yet what the ground itself reveals is quietly striking.

The passage does not simply stop at the entrance. Depressions and areas of collapse in the ground nearby suggest the structure extends roughly thirty metres eastward to the riverbank before turning northward for a short distance. That means most of the souterrain lies buried and partly fallen in, traceable only through the tell-tale hollows it leaves as the roof gives way over time. The proximity to the Kerry River on one side and a children's burial ground approximately twenty metres to the west adds a particular texture to the site. Children's burial grounds in Ireland, often called cilliní, were typically used from the medieval period onward to inter unbaptised infants, occupying a space that was marginal in both a physical and a social sense. That two such historically loaded features sit within a short distance of each other at Crossterry speaks to the depth of long-term activity in what now appears to be an unremarkable stretch of riverside woodland.

The site lies in wooded terrain with natural rock breaking through the surface in places, which gives some sense of the landscape as it might have appeared to whoever originally constructed the passage. The opening itself remains visible, and the stone steps are still discernible, though the collapsed sections make the full extent of the structure a matter of inference from the ground surface rather than direct observation.