Arch of Janus

The Arch of Janus is a four-sided antique gateway in the Velabrum valley near the Forum Boarium in Rome. Built in the fourth century AD, probably under Constantine or Constantius II, it is the only surviving quadrifrons arch in the city. It was constructed of brick and Roman concrete and originally faced largely with reused marble, a textbook example of late antique spolia. Long mis-attributed to the god Janus, scholars now suggest it marked a road junction and provided shelter for traders at the cattle market. The Frangipane noble family turned it into a fortified tower in the Middle Ages; the medieval superstructure was removed in 1830. Today the arch stands freely accessible at the corner of Via del Velabro and Via di S. Teodoro, next to the Cloaca Maxima and the church of San Giorgio in Velabro.