The iconic structure built in ancient Rome to hold gladiator fights is the Colosseum, also known as the Flavian Amphitheatre. Completed in AD 80 under Emperor Titus, this massive arena could hold tens of thousands of spectators and was primarily used for public spectacles such as gladiatorial combats, animal hunts, and mock sea battles. The Colosseum exemplifies Roman engineering and architectural prowess with its intricate systems of vaults and arches. It became a symbol of the empire's power and a popular venue for entertainment, representing both the grandeur and the darker aspects of Roman culture.