The construction of the Colosseum began during the reign of Emperor Vespasian in 70-72 AD. He wanted to build a grand amphitheater that would serve as a gift to the people of Rome and help restore the popularity of the weakened Flavian dynasty. However, the construction wasn't completely finished during Vespasian's reign, it continued during his son and successor, Emperor Titus, who finally inaugurated the amphitheater in 80 AD.