The arch is 21 m high, 25.9 m wide and 7.4 m deep. It has three archways, the central one being 11.5 m high and 6.5 m wide, the lateral archways 7.4 m by 3.4 m each. The top (called attic) is brickwork reveted with marble. A staircase formed in the thickness of the arch is entered from a door at some height from the ground, in the end towards the Palatine Hill.
The general design with a main part structured by detached columns and an attic with the main inscription above is modelled after the example of the Arch of Septimius Severus on the Roman Forum. It has been suggested that the lower part of the arch is re-used from an older monument, probably from the times of the emperor Hadrian (Conforto et al., 2001; for a defence of the view that the whole arch was constructed in the 4th century, see Pensabene & Panella).
During the Middle Ages, the Arch of Constantine was incorporated into one of the family strongholds of ancient Rome. Works of restoration were first carried out in the 18th century; 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.