Colosseum The Colosseum is an oval amphitheatre in the centre of the city of Rome, built of travertine limestone, tuff (volcanic rock), and brick-faced concrete, it was the largest amphitheatre ever built at the time and held 50,000 to 80,000 spectators. Construction began under the emperor <PERSON> in AD 72 and was completed in AD 80 under his successor and heir, <PERSON>.