A souterrain is an underground stone-lined passage or chamber associated with early medieval ringforts, typically interpreted as storage space, a refuge, or both. That one should end its life as the setting for a formal animal burial, constructed from the very stones of its own walls, is unusual enough to warrant attention.

The souterrain was uncovered during archaeological test excavation carried out ahead of the N5 Ballaghaderreen to Scramoge road project. It sat in the southern sector of a ringfort and measured roughly 4.12 metres east to west, 2.66 metres wide, and just under a metre deep. The chamber was earth-cut and lined with dry-stone walling of mostly limestone, with some sandstone included; the lower courses used very large stones, with horizontally laid flat slabs rising above them. Three stone steps descended from a sub-rectangular entrance on the south-east side. The roof had not survived and its original material remains unknown, though timber is considered a possibility. A fragment of fired clay recovered during excavation may be daub, suggesting some form of clay-plastered structure was once associated with it. The souterrain had at least two distinct phases of use: an original construction, then a later modification of noticeably lower quality that blocked the south-east entrance, opened a new ramped entrance to the north-west, and reduced the chamber's interior by nearly a third. Eventually the structure was filled with demolition rubble, including an iron blade and iron strap among other finds, and the surface was levelled so completely that no trace remained above ground. It was only after all of this that someone chose the south-west corner of the backfilled remains as the burial place for an adult dog, interred with evident deliberateness and care. No dating evidence was recovered from the burial, and the relationship between this act and the earlier phases of the site remains an open question.