What is the oldest thing in Rome and why is it significant to the city's history and culture?

The oldest thing in Rome is the Colosseum, which was built in 70-80 AD. It is significant to the city's history and culture because it was a symbol of Roman power and entertainment, hosting gladiator fights, animal hunts, and other spectacles that were important to Roman society. The Colosseum also represents the architectural and engineering achievements of the ancient Romans.