Ok now, walk back towards the Arch to the marble column base (square with reliefs and the round column base on top) on your left. It's called the 'Decennalia Base' and was a marble base that once supported an honorary column with a statue on top. It's one of a set of five that were on top of the Rostra (so not in its original location). In 303 AD Emperor Diocletian visited Rome for the first time, he ruled the eastern Empire and 'Maximian I' ruled the western Empire. This was the twentieth anniversary (Vicennalia) of their reign and the tenth anniversary (Decennalia) of the Tetrarchy (a four-Emperor system). Two Augusti (supreme rulers) Emperors, one in the East and one in the West and under each of them a Caesar (younger, vice-ruler) Emperor who would step in with the retirement or death of their Emperor, so no power-vacuum which often leads to civil war. It worked fine under Diocletian's reign but didn't last afterwards. Four of these 36 Roman Feet / 10.6 m / 35 feet high columns had one of the Emperors atop it but the center one was 40 Roman Feet / 11.8 m / 39 feet high with a statue of Jupiter atop it. I mentioned earlier the remains of these columns are behind the Custodian Shack, they are Rose-Pink Aswan Granite. Decennalia is a celebration started by Augustus in 17 BC where every ten years the Emperor celebrates his rule with Games, Circus', sacrifices, bloodsports and festivals.
This lone Decennalia base was found in 1547 near the Curia and setup here on a brick foundation in modern times. The brick foundation is built on a base of an unknown equestrian statue. The base doesn't align with the Rostra but is aligned with the Via Sacra and the Arch of Septimius Severus, it probably held a bronze equestrian statue of Severus or some later Emperor. The equestrian statue base on the other side of the Via Sacra in front of the Arch was dedicated to Constantius II in 352-3 AD.
The FRONT SIDE relief on the base shows two winged Victories holding up a shield on which is written 'CAESARUM DECENNALIA FELICITER' (Happy tenth Anniversary of the Caesars). Also people in captivity (POW's?) and booty (war trophies?).
The other three sides represent vows for another happy decade. The RIGHT SIDE relief shows 'Suovetaurilia', an animal sacrifice to the Gods of a boar, ram and bull. And they will be lead to sacrifice in that traditional order only. The attendant on the left is carrying the axe for the sacrifice, the toga clad man on the right is leading them. Farmers also do this type of sacrifice at an agricultural festival ever May. The farmer's family washes, dresses in white with olive wreaths and leads these animals around their fields three times and then sacrifices them. The animals entrails are then examined for omens, the entrails and bones are wrapped up and burned on an altar to the Gods. The meat is cooked and everyone eats very well at the festival. Except if you had sex the night before, you are then considered impure and can't join in. And of course the day before would be the day the wife would decide to strut around the hut with her new sexy hi-heeled sandals, a short low cut tunic and her new leather strophium (a leather band bra) :-) .
The LEFT SIDE relief shows a procession of toga clad Senators celebrating this Decennalia. In the background you can see four military standards (flags) being carried.
The REAR SIDE cannot be seen as the Forum is fenced-off and of course it's the best side :=(. It shows a Caesar Emperor at a sacrificial altar offering a libation while being crowned by a little winged Victory, behind him the toga clad Genius (spirit) of the Senate. Around him are the Gods Mars, Sol Invictus (Sun God) and a seated Roma also a toga clad bearded Augustus Emperor, priest with pointed headgear and an attendant. [You can see it with binoculars though.]
For more information and photos, please see Decennalia Base in A Tourist in Rome.
Next: #10: The Arch of Septimius Severus