It is a souterrain, a type of structure built during the early medieval period in Ireland, typically consisting of one or more dry-stone tunnels dug into the earth and roofed with large capstones. Their exact purposes are still debated among archaeologists, though most evidence points to a combination of uses: cool storage for dairy produce, refuge during periods of local conflict, or both. What makes the souterrain at Gorteens quietly notable is less what is known about it than what is not. The site is recorded as a monument, but the detail behind that designation remains, for now, largely inaccessible to the casual researcher.

Souterrains are found across Ireland in considerable numbers, with particular concentrations in the north and west, and County Mayo has its share. They tend to be associated with ringforts, the circular enclosed settlements that formed the basic unit of rural life in early medieval Ireland, though some souterrains exist independently of any visible surface enclosure. The Gorteens example sits within this broader tradition, a subterranean feature in a landscape that has been continuously farmed and modified for centuries. Without more specific documentary or excavation records currently available, the finer details of its construction, dimensions, or any finds associated with it remain unknown.