A souterrain is a dry-stone underground gallery, typically built during the early medieval period, and most were used for cool storage, refuge, or both. What makes this one quietly arresting is that it is now largely exposed to the open air, its roof and walls stripped back by centuries of collapse and encroachment, leaving the skeleton of the structure visible where it once would have been entirely concealed.

The souterrain sits within a cashel, a type of circular stone fort enclosed by a dry-stone wall, and the relationship between the two is typical of early medieval Irish settlement. The western end of the passage, just three metres long and barely half a metre high, is still roofed by three stone lintels, flat slabs laid horizontally across the walls in the simplest form of underground roofing. This appears to have been the original entrance point, though today it is heavily overgrown and surrounded by scattered rubble. From there the passage runs east a short distance before turning north for another three metres, where both side-walls survive but the structure is clogged with debris and the northern end of the western wall has deteriorated badly. The passage then turns east again for its longest section, five metres, with a maximum surviving height of one metre, though it too is filled with rubble and hemmed in on all sides. T. J. Westropp noted the site in 1898, and his record remains the earliest known reference to it.

The rubble throughout makes it difficult to trace the full course of the passage on the ground, but the three-part Z-plan is legible enough once you know what you are looking at. The lintelled western section is the most structurally coherent surviving portion, and the contrast between that carefully roofed entrance and the open, tumbled state of the rest gives a clear sense of how much has been lost above ground while the basic geometry of the design has endured.