​COLUMBARIUM (Lat. columba, a dove), a pigeon-house. The term is applied in architecture to those sepulchral chambers in and near Rome, the walls of which were sunk with small niches (columbaria) to receive the cinerary urns. Vitruvius (iv. 2) employs the term to signify the holes made in a wall to receive the ends of the timbers of a floor or roof.