Souterrains are artificial underground galleries built during the early medieval period in Ireland, typically associated with nearby settlement sites. They were constructed from dry stone, without mortar, and are thought to have served as places of refuge, storage, or both. What makes the Coad example quietly compelling is how little of it has actually been seen.

In 1995, a portion of the souterrain was uncovered, exposing a section of passage running roughly east to west. That exposed stretch measured 4.4 metres in length, which is modest, though the passage itself was only 0.6 metres wide at its base, barely enough to move through without turning sideways. The dry-stone walls rose to approximately 1.5 metres and leaned inward as they climbed, a corbelling technique that narrows the passage toward the top without requiring a flat capstone roof. At the western end, two stone-built steps were found, suggesting either a change in level within the underground system or a connection to a now-lost entrance. Beyond the uncovered section, the passage continues into the ground, its further course unexcavated and unmapped.