The site is recorded as having once contained a souterrain, an underground stone-lined passage or chamber typically associated with early medieval ringforts in Ireland, used variously for storage, refuge, or ventilation. There is nothing left to see. No depression in the ground, no collapsed stonework, no outline. Whatever was there has been entirely absorbed back into the landscape.

The sole record of the souterrain's existence comes from a 1934 observation by Bowman, who noted that such a passage had been present within the fort but was already destroyed by that point. The ringfort itself survives as a separate monument, but the souterrain it once contained is gone. The gap between when the passage was built, probably sometime in the early medieval period, and when Bowman documented its loss is complete. No earlier description appears to have been recorded, which means even a basic account of its dimensions, alignment, or construction is lost.