-Made from concrete core, brick around it, over the brick was stone facing travantine
-Columns that are integrated varied with the different styles: Tuscan(a form of Doric without fluting and with a base), ionic, Corinthian
-Events: fights, mock battles, ship races, executions
-Barrel vault with the arches the allow entrance
-Used concrete over stone because it's more flexible, moldable, didn't need skilled labor and quicker, then put on decoration.