<human>:  When did the Romans start building the Colosseum?
<bot>: The Colosseum was built between 72 and 80 AD. The Roman Emperor Vespasian ordered the construction of the Colosseum in 72 AD to celebrate his victory over the Jewish leader, Titus Flavius Vespasianus. The Colosseum was built in a hurry because Vespasian was very eager to celebrate his victory.