These structures, typically dating from roughly the seventh to the twelfth centuries, were constructed by hand, often lined with drystone walling and roofed with large flat slabs, then buried beneath the earth. Their precise purpose has been debated for generations; they may have served as places of refuge, as cool storage for perishables, or as a combination of both, sometimes connected to a ringfort or settlement above ground.

The souterrain at Coolnageragh is recorded as a monument, though the details of its construction, condition, and any associated features remain sparse in the available record. Kerry has a considerable concentration of such underground structures, which is itself a reflection of the density of early medieval settlement across the county. Without specific excavation data or detailed field notes attached to this particular site, what can be said is that its existence points to human activity in this landscape during a period when communities across Ireland were quietly engineering the ground beneath their feet, leaving cavities that have sometimes survived more than a thousand years of agriculture and change above them.