An inseparable feature of the Colosseum, the Arch of Constantine is thought to have been erected in 315 to commemorate Constantine's victory over Maxentius. Some of the decorative features were taken from earlier 2C monuments to be re-used on the arch. Recent studies suggest that this monument built in honour of Constantine was probably erected over a pre-existing arch built by Hadrian. Some of the decorative sculptures may then be from the same period as the original arch.