At Carrownrush in County Sligo, a souterrain, one of those narrow, stone-lined underground passages built during the early medieval period, typically for storage or refuge, is listed as existing within a rath, yet no visible trace of it remains on the surface.

The rath itself, a circular earthen enclosure of the kind that dots the Irish countryside in considerable numbers, survives at the site. These enclosures, often called ring forts, were the farmsteads and homesteads of early medieval Ireland, and it was common practice to incorporate a souterrain beneath or within them, the underground chamber accessible through a small entrance and used to keep food cool or to provide a place of concealment. The Carrownrush example is recorded in association with one such enclosure, but whatever once signalled the souterrain's presence, whether a capstone, a hollow in the ground, or a telltale depression in the earth, has since disappeared from view entirely.