A souterrain is a type of dry-stone underground passage or chamber, typically associated with early medieval ringforts in Ireland, and thought to have served for storage, refuge, or both. This one was discovered almost incidentally, a byproduct of a search that came up empty.

The excavation was carried out by Caulfield in 1850, with ogham stones as the target. Ogham is an early medieval script in which characters are carved as notched lines along the edge of a stone, and such stones turn up with some regularity in Cork and Kerry. None were found here. What Caulfield did uncover and record was a single chamber of stone construction, with, in his own words, "the flags of the ceiling supported by huge blocks of stone." The image he leaves is of something deliberate and substantial, a space built to last, roofed with heavy capstones in the manner typical of the souterrain tradition. The ringfort within which it sits remains a companion feature on the landscape, the above-ground enclosure and its underground annex once forming part of the same occupied site.