At barely a metre across, it gives little away on the surface, yet the evidence pulled from its fill points to something considerably more complex beneath. This is a probable souterrain entrance, a souterrain being an underground stone-lined passage or chamber constructed during the early medieval period, typically associated with ringforts and used for storage, refuge, or both.

Excavations carried out by M. Monk between 1981 and 1985 uncovered the pit in the north-east quadrant of the ringfort known as Lisleagh I. The pit extended beyond the edge of the excavated area, meaning its full extent was never exposed, and its western side had been cut into by what appeared to be a post hole, suggesting later activity had disturbed the original structure. The stony, voided fills inside sloped downward toward the boundary of the dig, a pattern consistent with a collapsed or partially infilled passage entrance. Among the finds was an unusual bronze buckle. Charred material recovered from the fill was radiocarbon dated to around 890 AD, placing it firmly in the later phases of early medieval Ireland. A resistivity survey conducted just north of the excavated area afterwards indicated the presence of a large, disturbed hollow feature underground, lending further weight to the idea that a more substantial passage lies beyond what was dug. Comparisons were drawn with souterrain entrances identified at Lisnagun in West Cork, a site where similar structural characteristics had been recorded.