A souterrain, to use the Irish archaeological term, is a man-made underground passage and chamber, typically built in the early medieval period using drystone construction, and thought to have served purposes ranging from storage to refuge. This one lay entirely unsuspected beneath a suburban development site until the ground simply gave way.

Excavated under urgent conditions by archaeologist Tony Cummins, the souterrain proved to be a fairly complete example of the type, built in an L-shaped trench. A passage running roughly east to west, some 6.38 metres long and just 1.1 metres high, was entered through a pit in the east wall. Its floor was cobbled with loosely packed, water-rolled stones, and its roof had been formed from lintels resting on corbel stones, most of which were already cracked before the dumper finished the job. At the western end of the passage, a narrow creepway, only 0.4 metres wide and roofed with three lintels, forced anyone moving through to squeeze into the rectangular chamber beyond. That chamber dropped sharply in floor level from the creepway, measured roughly 3.2 by 1.5 metres, and retained a small wall-press built into its west wall and an air-vent in the south wall. The roof over the chamber was sealed with smaller stones packed between four large lintels. The entrance pit had been deliberately backfilled at some point, and the soil used to block it contained sherds of nineteenth-century pottery. Cutting through that same deposit was a dumb-bell shaped stone-lined kiln of early modern date, extending northward from the souterrain, and it is possible that stones robbed from the souterrain's own walls and roof were reused in its construction. A second souterrain was found roughly 250 metres to the north-north-west as long ago as 1909, suggesting that this part of Cork's southside conceals, or once concealed, more than one such structure beneath what is now unremarkable suburban ground.