The Arco di Augusto is constructed from blocks of conglomerate. The arch has a single vault, with a height to the keystone of 11.4 metres. Its span is a barrel vault, constituting an extension in width of a round arch. In the monument, various styles can be recognised: The ten engaged columns which decorate its facade and its sides culminate in Corinthian capitals, while the entablature, adorned with metopes and triglyphs, is of the Doric order. In the Medieval period, it came to be called Saint-Voût (French for "Holy Arch") from an image of Jesus which was located in the same place.