The arch, which was constructed between 312 and 315 AD, was dedicated by the Senate to commemorate ten years (decennalia[b]) of Constantine's reign (306–337) and his victory over the then reigning emperor Maxentius (306–312) at the Battle of Milvian Bridge on 28 October 312, as described on its attic inscription, and officially opened on 25 July 315. Not only did the Roman senate give the arch for Constantine's victory, they also were celebrating decennia, a series of games that happens every decade for the Romans. On this occasion they also said many prayers. However, Constantine had actually entered Rome on 29 October 312, amidst great rejoicing, and the Senate then commissioned the monument. Constantine then left Rome within two months and did not return till 326.
The location, between the Palatine Hill and the Caelian Hill, spanned the ancient route of Roman triumphs (Via triumphalis) at its origin, where it diverged from the Via sacra. This route was that taken by the emperors when they entered the city in triumph. This route started at the Campus Martius, led through the Circus Maximus, and around the Palatine Hill; immediately after the Arch of Constantine, the procession would turn left at the Meta Sudans and march along the Via sacra to the Forum Romanum and on to the Capitoline Hill, passing through both the Arches of Titus and Septimius Severus.
During the Middle Ages, the Arch of Constantine was incorporated into one of the family strongholds of ancient Rome, as shown in the painting by Herman van Swanevelt, here. Works of restoration were first carried out in the 18th century,[c] the last excavations have taken place in the late 1990s, just before the Great Jubilee of 2000. The arch served as the finish line for the marathon athletic event for the 1960 Summer Olympics.
There has been much controversy over the origins of the arch, with some scholars claiming that it should no longer be referred to as Constantine's arch, but is in fact an earlier work from the time of Hadrian, reworked during Constantine's reign, or at least the lower part.[d] Another theory holds that it was erected, or at least started, by Maxentius,[e] and one scholar believed it was as early as the time of Domitian (81–96).
Whatever the faults of Maxentius, his reputation in Rome was influenced by his contributions to public building. By the time of his accession in 306 Rome was becoming increasingly irrelevant to the governance of the empire, most emperors choosing to live elsewhere and focusing on defending the fragile boundaries, where they frequently founded new cities. This factor contributed to his ability to seize power. By contrast Maxentius concentrated on restoring the capital, his epithet being conservator urbis suae (preserver of his city). Thus Constantine was perceived amongst other things as the deposer of one of the city's greatest benefactors, and needed to acquire legitimacy. Much controversy has surrounded the patronage of the public works of this period. Issuing a damnatio memoriae Constantine set out to systematically erase the memory of Maxentius. Consequently, there remains considerable uncertainty regarding the patronage of early fourth century public buildings, including the Arch of Constantine, which may originally have been an Arch of Maxentius.