In AD 303, five honorary columns were added behind the Rostra, as can be seen in its depiction on the Arch of Constantine. The first major structures to be erected in the Forum since the time of Septimius Severus, they celebrated the tenth anniversary of the Tetrarchy, which was the occasion of Diocletian's only visit to Rome as emperor. All of pink granite from Aswan, the middle, taller one carried a statue of Jupiter, the others, the four rulers of the empire (two Augusti and two younger Caesars).
One of the marble pedestals, the so-called Decennalia Base, was discovered in 1547 and has been placed nearby on the Via Sacra. In this view, two winged victories hold a shield on which is inscribed CAESARUM DECENNALIA FELICITER, "Happy Tenth Anniversary of the Caesars." A bull, sheep, and pig, all accompanied by attendants, also are depicted. The most important animals of the farm, they were the traditional sacrifice to Mars, when the god had been an agricultural as well as a martial deity. Opposite this scene is a procession of senators. Facing away from the Via Sacra and not readily visible is the principal side, which shows the Caesar, a Victory flying to crown him, making a libation in front of an altar and surrounded by a priest and personifications of Mars, the Senate, Roma, and the Sun.
