What was the Colosseum built on the site of?

The Colosseum was built on the site of Nero’s artificial lake. After the Great Fire of Rome in AD 64, Emperor Nero created the vast Domus Aurea complex, including a private lake surrounded by gardens, pavilions and porticoes.

When the Flavian dynasty came to power, Vespasian began dismantling much of Nero’s extravagant palace complex and filled in the lake. He placed the new amphitheatre there as a deliberate political statement: land that Nero had appropriated for personal luxury would be returned to public use. The site’s central position between Rome’s Caelian, Esquiline and Palatine hills also made it practical for a huge urban venue.

Construction began around AD 70–72, and Titus completed the amphitheatre in AD 80. The Colosseum was therefore not built on the Circus Maximus, which was a separate chariot-racing stadium, nor on the Campus Martius. The nearby Domus Aurea palace explains the connection, but the specific feature replaced by the amphitheatre was Nero’s artificial lake.