The Colosseum in Rome is the largest ancient amphitheater ever built. Completed in 80 AD under Emperor Titus, it could hold an estimated 50,000 to 80,000 spectators. While famous for gladiatorial contests, it also featured 'naumachia' or simulated sea battles, where the arena floor was flooded with water. The most complex part of the structure was the 'hypogeum'—an underground network of tunnels and cages used to house animals and gladiators before they were hoisted to the surface via manual elevators. The exterior features a vertical stack of the three classical architectural orders: Doric on the ground floor, Ionic in the middle, and Corinthian on the top. Despite damage from earthquakes and stone-robbers, the Colosseum remains an iconic symbol of Imperial Rome and is one of the New Seven Wonders of the World.