Construction of the Colosseum began under the rule of Emperor Vespasian[1] in 72. It was completed by his son, Titus, in 80[1], with later improvements by Domitian. It was built at the site of Nero's lake below his extensive palace, the Domus Aurea, which had been built covering the slope of the Palatine after the great fire of Rome in 64. Dio Cassius recounts that 9,000 wild animals were killed in the one hundred days of celebration which inaugurated the amphitheatre opening.
After the Colosseum's first two years in operation, Vespasian's younger son (the newly-designated Emperor Domitian) decided to sacrifice the ability to flood the arena in return for a hypogeum.