What the collapses reveal is a souterrain, an underground stone-lined passage of the kind constructed throughout early medieval Ireland, most often as a place of refuge or storage beneath or beside a settlement. Here, three lintels, the flat capstones that would once have roofed the passage, are now visible at the surface, and where they have shifted apart the passage beneath can be partially seen, its walls still standing, its floor silted up over centuries.

The souterrain sits in the south-western quadrant of a cashel, a type of stone-walled enclosure used as a defended farmstead in early medieval Ireland, and the two structures almost certainly belong to the same period of occupation. The passage runs on a north-west to south-east axis. Beyond that orientation, the silt that has accumulated inside it keeps its full extent, and whatever it once contained, out of reach for now.