The field gives nothing away, bar the occasional outcropping of bare rock breaking through the grass, and yet underneath lies a souterrain, an underground stone-built or rock-cut passage structure associated with early medieval settlement in Ireland, typically used for storage, refuge, or both.

The structure was documented by McCarthy in 1977, and what was recorded is a precisely articulated underground arrangement. Two sub-rectangular chambers, each between roughly three and three and a half metres in length, run on a northwest to southeast axis. A passage approaches chamber one from the northwest, and a creepway, a low connecting passage requiring a person to crouch or crawl through, links chamber one to chamber two at its northeastern end. This kind of internal arrangement, with deliberately restricted access between spaces, is characteristic of souterrains built during the early medieval period in Ireland, where the awkward crawl through a creepway would have slowed any unwanted entry considerably.