The Colosseum’s exterior has three rows of arches.
These are the three superposed arcaded storeys that form the best-known part of the façade. Each level uses a different classical order of engaged columns: Doric on the ground floor, Ionic on the second, and Corinthian on the third. The stacked arrangement gives the building its distinctive rhythm of arches and columns.
Above the three arcaded levels is an attic, or fourth exterior zone. It is not another row of arches in the same sense. The attic was pierced by windows and supported the equipment for the velarium, the retractable awning that shaded spectators. This is why descriptions can mention four levels while the answer to the arches question remains three.
The Colosseum’s arches were practical as well as decorative. They opened into a network of corridors, stairways, and vaulted passageways that distributed spectators through the building. The ground-level entrances were especially important for rapid crowd movement.
The columns also display Roman architectural design at a glance: the lower levels progress from Doric to Ionic to Corinthian, while the attic uses Corinthian pilasters. The visible three-arcade façade is therefore both an engineering system and a carefully staged monument.