That hollow, however, is the point. Bullaun stones are boulders or outcrops bearing one or more cup-shaped depressions, ground or worn into the surface, and they appear across Ireland in considerable numbers, often near early medieval ecclesiastical sites. Their exact purpose remains a matter of debate: some may have been used for grinding or processing, others seem to have accumulated ritual or votive significance over centuries, gathering associations with healing, cursing, and the veneration of local saints that lasted long after the medieval period ended.