Arch of Constantine was commissioned by the (then) Roman Senate to honour Constantine’s victory in the battle of Milvian Bridge in 312CE. Constantine defeated Maxentius in the battle. Today there are only three triumphal arches in Rome that have survived, Arch of Constantine being one of the three and also the largest one.

The Arch of Constantine is situated between the Colosseum and the Palatine Hill. It was dedicated to Constantine on the 10th anniversary of his reign in 315CE. The arch goes as high as 21 meters and stretches up to 25.6 meters.
Structure of the Arch of Constantine
The layout of the main facade is same on both the sides of the arch. The arch is made of white and grey proconnesian marble and is divided into three separate arches; the main arch in the middle with two half sized arches on each side. Carved in the monument are corinthian columns on each side of the arches, making it four in total. Standing on pedestals these columns are made of numidian yellow marbles. On the top of the columns are entablature.
On the Arch of Constantine, one can see pedestals above all four entablatures. On those pedestals are statues representing Dacians. Then there can be seen a pair of reliefs in between the statues, above the entablature of minor arches. Also there are a couple of pair or reliefs just above the minor arches and below the entablature. Similar reliefs can be seen on the other side of the arch too. These reliefs were taken from some other existing (unknown) monument as to decorate the arch.
Many of the sculptures decorated on the arch are from other triumphal arches. These arches were of Trajan, Hadrian and Marcus Aurelius. The sculptures taken from these arches consisted of some reliefs and statues.

Under the round reliefs are the friezes. These friezes are prime additions on the arch from the Constantine’s time. These friezes depicts the scene from the Constantine’s camp against Maxentius.
Inscription on the Arch of Constantine
If one sees, there is an inscription on the middle of the top of the arch, which is common on arches. This Latin inscription is written on both the sides of the arch.
It reads; | And means; |
IMP CAES FL CONSTANTINO MAXIMO P F AUGUSTO SPQR QUOD INSTINCTU DIVINITATIS MENTIS MAGNITUDINE CUM EXERCITU SUO TAM DE TYRANNO QUAM DE OMNI EIUS FACTIONE UNO TEMPORE IUSTIS REM PUBLICAM ULTUS EST ARMIS ARCUM TRIUMPHIS INSIGNEM DICAVIT | To the emperor Flavius Constantine the Great, pious and fortunate, the Senate and People of Rome because by divine inspiration and his own greatness of spirit with his army on both the tyrant and all his faction at once in rightful battle he avenged the State dedicated this arch as a mark of triumph. |
However, this is not the only inscription on the arch, there are two mini inscriptions on the inside of the central arch and one above both the side arches.
The inscription inside the central archway reads; “liberatori vrbis” and “fundatori qvietis“, meaning “liberator of the city” and “founder of peace” respectively. Whereas, the inscriptions on the side arches reads; “votis x — votis xx” and “sic x — sic xx“.