The building was begun by Vespasian in AD 72, and after his son Titus enlarged it by adding the fourth story, it was inaugurated in the year AD 80 with a series of splendid games. The Colosseum was large enough for theatrical performances, festivals, circuses, or games, which the Imperial Court and high officials watched from the lowest level, aristocratic Roman families on the second, the populace on the third and fourth.
Beside the Colosseum stands the almost equally familiar Arch of Constantine, a triumphal arch erected by the Senate to honor the emperor as “liberator of the city and bringer of peace” after his victory in the battle of the Milvian Bridge in 312.
The purpose of the Colosseum and the reason the Flavian emperors constructed it was to satisfy the public enthusiasm for games and spectacles. But the emperors and nobility also attended, each watching from a level determined by rank. The emperor and the Vestal Virgins had the best views from boxes at the north and south ends of the arena, and you can still see the names of senators carved in the stone of the area between these, which was reserved for them.
Noble families sat on the second course, and the general public sat in the third and fourth levels. Rows of seating and internal passages and staircases were carefully arranged, so the 50,000 spectators could get to their places or leave within a few minutes.
On the top level, there were originally 240 masts set around the walls that supported an awning over the audience. The entire interior was lavishly decorated, but only a few fragments survive to hint at what it must have looked like in the first centuries.
A bronze cross at one end of the arena commemorates the Christian martyrs who were believed to have died here during the Roman Imperial period. In fact, there is little evidence that the arena was used for this, and the first mention of it as a place of Christian martyrdom was not until the 16th century.
The arena floor was 83 by 48 meters, built of wood, and covered with sand. It has long since been destroyed, so you can now see the walls of the hypogeum, a vast two-story underground labyrinth of tunnels connecting training rooms for gladiators, cages for exotic wild animals, and store-rooms that were hidden underneath the floor.
Elaborate machines lifted scenery and caged animals to the arena, and according to accounts of the period, the arena was sometimes filled with water for mock sea battles.