A souterrain is a man-made underground passage or chamber, typically built from drystone walling and covered with lintels, used in early Christian-period Ireland for storage, refuge, or both. Most are only detectable at the surface as subtle depressions, and this one is no different, its shape tracing the outline of whatever corridor or chamber system once lay beneath.

The depression runs in two directions: a longer axis of roughly 7.2 metres oriented north to south, and a shorter arm of about 5.7 metres extending eastward from its northern end, giving the whole feature a total measurable length of more than 12.9 metres. Traces of drystone walling are still visible intermittently along its edges, suggesting the structure beneath has not fully collapsed. A separate linear depression about a metre to the east, measuring nearly 4.8 metres in length, is thought to be associated, possibly a second passage or a related feature. The souterrain sits within the north-western quadrant of a rath, the term for a roughly circular earthwork enclosure, typically a farmstead of the early medieval period, surrounded by one or more banks and ditches. Finding a souterrain inside a rath is entirely in keeping with the pattern across Ireland, where such underground features were routinely incorporated into the domestic layout of these enclosed settlements.