It is a souterrain, a type of structure built during the early medieval period, roughly between the sixth and twelfth centuries, typically by hand-laying dry stone to form narrow tunnels or chambers just below ground level. Their precise purpose remains debated among archaeologists: they may have served as cool storage for food, as places of refuge, or as both at different times. The Graigue example is one of hundreds recorded across Ireland, though Sligo as a county has a comparatively modest concentration of them, which makes each individual site of some interest.

Beyond its existence as a recorded monument, the specific history of this particular souterrain, its dimensions, its construction details, and any finds or disturbances associated with it, remains to be formally documented in any publicly accessible form. What can be said is that souterrains are almost always found in association with early medieval settlement, often close to a ringfort or rath, the circular enclosed farmsteads that were the dominant form of rural habitation in Ireland during that period. The townland name Graigue, derived from the Irish word for a small settlement or hamlet, fits neatly with this pattern, suggesting a landscape that has been continuously, if quietly, occupied for well over a thousand years.