The structure is a souterrain, an underground chamber or tunnel built using drystone construction, that is, stones laid without mortar, and it stretches 16.8 metres from north to south. These features appear throughout early medieval Ireland, typically associated with ringforts, the circular enclosed farmsteads that once dotted the countryside. Their exact purposes are still debated, but most were used for storage, refuge, or both.

This particular souterrain sits within the southwest quadrant of the adjacent ringfort, a spatial arrangement that was not unusual, since such passages were often positioned close to the interior edge of a fort's enclosing bank. The chamber runs on a NNE-SSW alignment, and while the northern end has collapsed inward, reducing that section to exposed side-walls, the southern portion retains its roof. That intact southern section can still be entered from the point of collapse, making this a site where the transition from ruin to preservation is something you can almost step across.