This is a souterrain, an underground stone-lined tunnel typically constructed during the early medieval period in Ireland, most likely serving as a place of refuge, storage, or concealment. What makes this one quietly interesting is its position: not tucked into the outer wall of the enclosure, as souterrains commonly are, but sitting towards the centre of the fort itself.

The ringfort here, known as a rath, a roughly circular enclosure defined by an earthen bank and ditch, occupies the northern edge of a plateau. Within it, the souterrain runs for about 4.8 metres on an east-west axis and stretches some 2.1 metres across. At its western end the passage bends northward, where a short stretch of perhaps a metre retains some of its original roofing before the tunnel becomes blocked and impassable. A second souterrain lies in the western perimeter of the same rath, which is not unusual; ringforts with multiple underground features are known elsewhere in Ireland, suggesting that the community using this enclosure had particular reason to invest in subsurface construction, whether for storing perishables in the cool earth or for the more urgent purpose of disappearing quickly when circumstances required it.