Roman gladiators fought in wooden amphitheaters until 80 A.D. when the first stone structure called the "amphitheatrum flavium", or more commonly known as the colosseum, was constructed. The gladiators would fight on the "harena" sand in the center of the colosseum.
The blood-soaking harena sand became such a defining characteristic of the colosseum and the gladiator games that the center of the colosseum was eventually termed the "arena." The colosseum measured nearly 160 feet tall and 6 acres in diameter. It is generally accepted that the colosseum could hold nearly 87,000 spectators when filled to its capacity. The doors that allowed spectators to enter and exit the colosseum were known as the vomitoria.