At just 0.63 metres across, the opening into this souterrain, an underground stone-lined tunnel typically associated with early medieval settlement in Ireland, gives little away about what lies beyond. The passage itself extends roughly 4.3 metres in a southeast to northwest direction, constructed in drystone, meaning the walls are built from carefully arranged unmortered stone. Its northwestern end closes with a neat, squared-off wall, and the southeastern entrance is currently choked with collapse, making it impassable. What is particularly intriguing is the stone-lined depression just outside that entrance, which suggests the souterrain once extended further than its current accessible length.

Souterrains of this kind were commonly built during the early medieval period in Ireland, roughly between the seventh and twelfth centuries, and are frequently found in association with earthworks. Here, the structure sits within exactly such an enclosure, the earthwork recorded separately in the local archaeological record. The original function of souterrains is still debated among archaeologists: they may have served as places of refuge, as cool storage spaces for food and dairy, or as a combination of the two. The Gortnaporia example, though modest in scale, fits this broader pattern well, a utilitarian underground feature quietly embedded in the landscape, its full original extent now a matter of inference rather than certainty.