The Arch of Janus is a four-sided arch (ie with four arches ) in Rome. Still preserved, is at the church of San Giorgio al Velabrum , not far from the Temple of Hercules and the Temple of Portunus , and was built on the edge of the Forum Boarium probably the mid-fourth century. Probably to be identified with the Arcus Divi Constantini cited by Regional Catalogues at the Velabrum .

The modern name does not refer to the two-faced god Janus, but rather derives from the Latin word ianus , indicating a covered walkway, or a door. As witnessed by the iani sources in the Roman Forum , it was not a triumphal arch , but probably of a structure intended to bankers operating in the Forum Boarium .

The building has a square (12 m wide by 16 m high ) with four massive pillars supporting a vault , built with cement and covered with marble blocks for reuse . Above must submit a crown , perhaps in the shape of a pyramid , whose structure in brickwork , which was originally to be equally covered with marble, was demolished in 1827 because it wrongly considered to be part of the medieval fortress implanted over the building to the Roman work Frangipane ( who had also closed the tubes ) .

Outside the piers are home to two rows of three niches on each side (total 48) , originally framed by small niches with columns supported by brackets , now lost . The niches , covered by a half dome shell carved in marble blocks of the coating, were originally accommodate statues. The only surviving remains of the sculptural decoration are represented by the four female figures on keystones : recognize with certainty the goddess Minerva in Rome on the eastern side and on the northern side , while the identification of two other figures such as Juno and Ceres presents more uncertainties
The Arc functions as well as having served as a monumental shelter dall'inclemenza time to Roman merchants who thronged the Forum.



During the Middle Ages , the Roman family of the Frangipane used it as a fortress by closing the tubes , and when these works were eliminated in 1830 , were lost even the attic and top the original , because they were recognized as works belonging to the original structure . In the nearby church of San Giorgio al Velabrum preserved some fragments of a monumental inscription , no longer be reconstructed , partly reused as building blocks of masonry and partly to medieval reliefs , which may have been the one present in the attic of the arch. It alludes to a tyrant defeated by an emperor and could refer to Constantius II and his victory over Magnentius . If this had confirmed the work could be reconsidered as a triumphal arch.