A small opening is all that gives the structure away, hinting at an earth-cut chamber that extends southward under the bank and possibly turns northwest beneath the interior of the fort above. The word "inaccessible" in the archaeological record is doing a lot of work here; this is not a place that rewards a closer look so much as one that rewards the imagination.

The souterrain sits within the southern half of a ringfort, the kind of enclosed farmstead that appears in its thousands across Ireland, typically dating from the early medieval period, roughly the sixth to the twelfth centuries. Souterrains, which are underground stone-lined or earth-cut passages and chambers built beneath or beside these settlements, are reasonably common features of ringforts throughout Munster and beyond, though their precise function is still debated. Storage, refuge, ventilation for a dwelling above, possibly all three at different times. What makes the Cnoc An Iúir example quietly notable is its apparent extent and its orientation, running under the bank and possibly looping back under the interior, suggesting a more complex layout than a simple dead-end chamber. Without excavation, the full shape of the passage remains unknown.