To prepare the building site, it was first drained as a precaution against potential earthquake damage. The foundation was set six meters deep to ensure the structure's stability (Cartwright). Three stories in height, the exterior of the Colosseum was distinctive with eighty arched entrances supported by columns that were semi-circular. The columns in each story of the Colosseum were of a different style. The bottom story contained columns that were of the Doric order, a relatively simple design. The second story contained columns that were of the Corinthian order, an ionic and ornate design. Built in A.D. 315, the main entrance contained the Arch of Constantine, which was commissioned to commemorate Constantine I's conquest of Maxentius (History.com Staff). Architecturally, the facade of the Colosseum is a mixture of Roman arches and Greek columns with a Tuscan flair on the lowest story. In the interior, builders constructed a complex system of concrete barrel vaults to hold up the colossal oval seating area (Kleiner). The circular design of the Colosseum ensured that all spectators were able to see the events that occurred in the center of the arena.
The Colosseum was constructed to seat more than 50,000 spectators, although it housed 50,000 vaulted seats. The spectators were most likely seated according to their social ranking. Spectators who hailed from the upper echelon received the best seating and were most likely far removed from the spectators of the lower social ranks. These spectators were perhaps also secluded in a comfortable area with their servants providing food, drinks, and other comforts. Spectators who hailed from a lower social ranking received the worst seating and were most likely crammed tightly together. The top story of the Colosseum unfurled awnings to shield spectators from the high temperatures of the blazing sun as they watched fights between wild animal, scavenger hunts, gladiatorial battles, and mock naval engagements.