The History of Rome
The colesseum was used as an stadium for the gladiators to fight. That was the cities entertainment. They filled the stadium up with water and navy fights too, but they only did that for about a year. The colosseum gave gladiators a permanent killing field.
Gladiators were slaves trained to fight to the death. After winning they were set free. The colosseum was a permanent killing field for the gladiators.
Rome wanted to show that they were as grand as Greece. The Romans created the Arch also. Rome is also the ones who created the domes and concrete.