The Five-Columns monument is most widely recognized for its only preserved marble
plinth, called the
decennalia base. With relief carvings of ceremonial and ritual scenes on all four sides, this column base was uncovered in 1547 and now stands close to the findspot. The side with the
decennalia inscription, from which the base name derives, is agreed to have been the most prominent side of the plinth. As for the other three sides, scholars vary in the order of their descriptions. Together, these reliefs represent the rites involved with taking vows for another decade of Tetrarchic reign. Some scholars have observed a sequence among the panel reliefs in which the animals are being led toward the sacrificial altar, with the imperial procession also heading for the altar scene.
The inscribed side This northern side faces the via Sacra, and in its center, two winged
Victories hold a shield with the inscription “
Caesarum decennalia feliciter,” celebrating the tenth anniversary of the
Caesares. However, neither emperor is identified specifically, a fact which Kalas believes “anticipated the continuity of joint rulership beyond the first Tetrarchy”.
Imperial sacrifice side This southern side shows a small Victory crowning emperor, though unclear which one, making a libation at the altar of
Mars. The god himself watches over the event from the left. The
flamen Martialis priest, as identified by his pointed cap, stands between Mars and Victory. Positioned in front of the
flamen is one child bearing the incense box and another playing flutes or pipes. To the emperor's right is a toga-clad personification of the
Senate,
genius senatus, with another senator on the far left of the scene. On the far right of the sacrifice are a headless seated
Roma and a radiant
Sol Invictus, who as a pair symbolize eternal Rome. Together with Mars and Victory, the emperor's offering unites military victory with the eternal glory of Rome.
Suovetaurilia side This western side depicts a scene of preparations of a bull, sheep, and pig for sacrificial offering, in a ritual called the
suovetaurilia. With the animals are attendants and a priest to perform the sacrifice, as part of the Tetrarchic decennial vows.
Senatorial procession side This eastern side, facing the rest of the Forum, shows a procession of Roman senators. Four of them are carrying banners, which may be representative of honors for all four Tetrarchs. ==Other fragments==