The Arch of Constantine is the largest triumphal arch of the imperial era that has survived to this day. It was dedicated by the Senate to commemorate Constantine's victory against Maxentius in the battle of the Milvian Bridge (28 October 312), as can be read from the inscription repeated on the two facades of the attic: "IMP(ERATORI) CAES(ARI) FL(AVIO) CONSTANTINO MAXIMO P(IO) F(ELICI) AUGUSTO S(ENATUS) P(OPULUS) Q(UE) R(OMANUS) 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", that is: "To the Emperor Caesar Flavius ​​Constantine Maximus, Pius, Felix, Augustus, the Senate and the Roman People dedicated this arch "He was renowned for his triumphs because, through the inspiration of divinity and the greatness of his spirit, he and his army avenged the state both from the tyrant and from every faction with just weapons."

The arch has three arches, the central one being the largest, outlined by four Corinthian marble columns. The facades are covered with relief decorations: sculptures depicting Victories with trophies and captive barbarians, river deities, and some allegorical figures.

In particular, the statues of captive Dacians date back to the Trajan era (with their heads remade in the 18th century), while the eight tondi placed above the lateral arches belong to the Roman era. of Hadrian and depict hunting scenes and sacrifices: the departure for the hunt, a sacrifice to Silvanus, the bear hunt, a sacrifice to Diana, the boar hunt, a sacrifice to Apollo, the lion hunt, and a sacrifice to Hercules.