The ancient Roman structure used for gladiatorial contests was the Colosseum, also known as the Flavian Amphitheatre. Completed in AD 80, it was an architectural marvel of its time and could hold tens of thousands of spectators. The Colosseum hosted various forms of entertainment, including gladiatorial games, animal hunts, and mock sea battles. These events were integral to Roman culture and served to demonstrate the power of the empire. The Colosseum remains a symbol of Rome's architectural and engineering prowess, as well as its complex social dynamics, showcasing both the grandeur of the empire and the brutality of its entertainment.