The triumphal arch, usually built to commemorate a victory in war or an important event, first appeared in Ancient Rome as a purely celebratory element and was then widely used in the Imperial age. Its shape is that of a large arch-shaped doorway. It may have one or more fornixes, i.e. openings, and have decorations and reliefs. In ecclesiastical architecture, the triumphal arch separates the nave from the presbytery, that is, the space of the faithful from the space of God.