These structures were usually drystone-built, roofed with large lintels, and concealed beneath the surface, which is precisely what makes them easy to overlook and, when one is eventually located, quietly remarkable.

Beyond the fact of its existence and location, the specific details of this particular souterrain remain largely inaccessible at present. What can be said is that souterrains in Connacht tend to be associated with ringfort settlements of the early medieval period, roughly the sixth to the twelfth centuries, and Galway has yielded a number of them across its townlands. Ballinastack itself is a small rural townland, the kind of place where field boundaries and subtle ground depressions can still hint at the buried architecture of an older landscape.