Colosseum

The Colosseum in Rome (70-82) is best known for its multi-level system of vaults made of concrete. It is called the Colosseum after a colossal statue of Nero that once stood nearby, but its real name is the Flavian Amphitheatre. It was used for staged battles between lions and Christians, among other spectacles, and is one of the most famous pieces of architecture in the world.