What makes it worth a second look is the opening exposed in its south-western wall: a lintelled entrance, the kind of stone-roofed passage characteristic of a souterrain, leading into a small semicircular chamber built in drystone without mortar. A souterrain is an underground stone-lined passage or chamber, typically associated with early medieval settlement in Ireland, and thought to have served for storage, refuge, or both. This one is modest in scale, the visible chamber measuring roughly 1.4 metres east to west and little more than half a metre high, partly filled with accumulated earth. A large slab lying close to the entrance was probably once a lintel, displaced at some point by collapse or interference.

The site went unrecorded on the Ordnance Survey's six-inch map of 1838, which suggests it was either unnoticed or already so unobtrusive as to escape the attention of surveyors. By the time the 1916 edition was produced, it had been identified and marked simply as "Souterrain". Local tradition holds that there are two chambers rather than one, the second presumably lying further into the ridge beneath the soil and the low earthen mound that borders the pit to the north. Whether that second chamber survives intact, or has collapsed under the weight of centuries of pasture, is not known. The ridge itself sits between areas of low-lying, wettish ground and bog to the north and south, the kind of marginal landscape that was nonetheless often chosen in early medieval Ireland for its slight elevation above the damp.