The southern face of the quarry now reveals, in cross-section, at least three stone-built chambers belonging to a souterrain, the kind of subterranean structure, typically constructed of drystone walling and roofed with large flat lintels, that was built across early medieval Ireland for storage or refuge. What makes this particular example quietly strange is the way it was revealed: not through excavation, but through industrial cutting that sliced the structure open like a diagram, leaving its chambers exposed to view from the side rather than from above or within.

The field in which the quarry sits was recorded as 'Parknakilla' on Ordnance Survey maps from 1900 to 1901, a name that offers no immediate clue to what lay beneath it. Of the three chambers now visible, the first is orientated north to south and extends back into the quarry face, with one wall of drystone construction and the other formed partly by a single upright slab. A large roof lintel survives in place, sitting roughly a metre below the present ground surface. Whether the stone blocking the chamber's southern end is the original end wall or a lintel that has since collapsed remains uncertain. The second chamber, running east to west along the quarry face, survives only in fragments: two upright slabs forming part of its northern wall and two roof lintels above. The third chamber, oriented roughly northeast to southwest, is represented by just two upright slabs, probably from its eastern wall. The first two chambers are partially filled with earth and gravel, which has both preserved and obscured whatever else may remain.

The site sits in a working or former quarry, and the souterrain is visible in the quarry's southern face. The chambers are largely inaccessible given their partial infill and the manner of their exposure, but the structural details, upright slabs, surviving lintels, and drystone walling, can be read in section. The overall extent of the souterrain beyond what the quarrying revealed is unknown.