A souterrain is an underground stone-lined passage, typically associated with early medieval settlement and used variously for storage, refuge, or concealment. This one has not been seen in living memory. By 1981 there were no surface remains visible, and the precise location of what local people remembered simply as a "cave" had already been lost. The monument exists now primarily as an outline on an old map, a narrow trench measuring roughly 28 metres long and 7 metres wide, running east to west, as recorded on the revised 1913 edition of the Ordnance Survey six-inch map.

The cartographic trace is the clearest evidence that something was once here. Whether the original surveyors were recording a visible depression, a partially collapsed passage, or simply a feature already well known to local farmers is not recorded. About 40 metres to the north, a standing stone still occupies the same field system, and its survival alongside the souterrain's disappearance is its own quiet puzzle. Standing stones and souterrains do not have an obvious functional relationship, but their proximity in the landscape suggests this corner of Westmeath was used and marked across a long stretch of time, with the underground feature eventually yielding entirely to the soil above it.