A souterrain, to give it its proper name, is a man-made underground tunnel or chamber, typically associated with early medieval ringforts and raths in Ireland, and thought to have served for storage, refuge, or both. What makes this one immediately striking is that it has been dug out entirely, leaving its former course exposed as a flat-bottomed, vertically sided cut in the earth, roughly twelve metres long, two and a half metres wide at the top, and about eighty centimetres deep, running on a northwest to southeast axis.

The souterrain extends inward from the western bank of the rath itself, which carries the separate monument reference SL013-015001-. Raths are the remains of enclosed farmsteads from the early medieval period, defined by one or more earthen banks and ditches. Here, the relationship between the enclosure and its underground feature is still readable in the landscape, even in this exposed state. A drystone field wall, constructed at some point after the monument fell out of use, crosses the trench near its northwestern end and divides the interior of the rath, a reminder of how later agricultural activity has layered itself over much older ground.