The Arch of Constantine, the largest triumphal arch of Rome, is in front of the entrance to the Coliseum. In the Roman Forum there remained three triumphal arches and the Arch of Constantine is the latest of them. It was erected in 315 A.D. The nearby arches of Titus and Septimius were built in 81 A.D. and 205 A.D., respectively.
Under the emperor Constantine Christianity was made the official religion of the Roman Empire. This defined the further development of the western civilization. In history this emperor is known as Constantine the Great. However, he might not become an emperor.
Constantine was born in 272 A.D. and after the death of his father, in 306 A.D., he was declared emperor. However, Maxentius, supported by the Praetorian Guard, seized the power and ruled over Rome to 312 A.D.
On October, 28 312 A.D. Constantine defeated Maxentius in the Battle of the Milvian Bridge and became a single ruler of the Roman Empire. Historically, the battle was very important. Having become the emperor Constantine first immediately legalized Christianity and then, in 370 A.D., made it the official religion of the Western Roman Empire.
In 315 it was decided to erect the triumphal arch (the Arch of Constantine) in honor of the Battle of the Milvian Bridge. The arch is 21 meters high and 25.7 meters wide. The depth of the arch is 7.4 meters, which is a bit more than that of the Arch of Septimius. The Arch of Constantine has three spans and is trimmed with marble. Nearly all bas-reliefs were taken from the other earlier structures.