Ok now, look behind (to the east of) the Hole and you will see a small equestrian pedestal base with some short column fragments lying on the right side (south) of the raised base. It's the flat grey slab of stone just to the upper-right of the Hole in this photo. Not the brown columns lying on their side, but the flat grey slab.
It's *possible* that this is the base for the bronze equestrian statue of 'Constantine the Great' (Equus Constantini). In 312 AD Constantine kicked Emperor Maxentius butt and became Emperor of the Western Roman Empire and the first (semi-)Christian Emperor. And in 324 became the Emperor of both the Western and Eastern Empires. He also built the first St. Peter's Basilica.
In 334 AD Anicius Paulinus (Consul Ordinarius and Praefectus Urbi) dedicated an equestrian statue of Constantine in the middle of the Forum Square. Whether this is that statue's pedestal base is not known for certain but it did have a very honorable location which was directly centered on axis with the 'Late Imperial Rostra' which occupied the eastern end of the Forum Square.
That Rostra was mostly mistakenly destroyed during the early excavations thinking that it was a Medieval building. The pedestal is of very shoddy workmanship even for Constantine's time (remember Rome is in decline and the real power now lies in the west... Constantinople). The concrete and brick core sits directly on the Forum pavement with three reused blocks of travertine forming the top. And on top of the travertine blocks cut fragments of marble columns were placed (I assume those lying on the ground next to the base, reused Numidian Yellow columns). Times are tough, I wonder if the bronze equestrian statue was really cast just for Constantine or a reused older statue just renamed?
Before you leave this area which is the only section where you can actually stand in the fenced-off Forum Square just try to imagine. In the about 1200 years from the draining of the marsh and turning this into dry land to the last monument dedicated in 608 AD what went on here and who walked upon this football field size area. Become part of the crowds cheering Rome's latest victory or trembling at the news of a defeat. The riots, civil wars, invasions, political murders and the military triumphs that happened here. Kings, dictators, Emperors, historical figures, etc addressing the cheering, jeering or fearful crowds gathered here and where many historical persons had their funerals. And a million untold stories of those who walked over this same Square be they royalty, slave, citizen, rich, poor, lover, villain, saint, etc.
'The Butterfly Effect' of what happened or didn't happen here severely impacted how our modern World turned out. March 15, 44 BC late morning: Julius Caesar's litter passes through the Forum Square in his hand is a note that was just given to him that warns him that he will be assassinated at the Senate meeting. He never read the note. If he had read it while passing through the Forum, the World's history as we know it would have been drastically changed right up to the present day. And you would not be reading this because I never existed and neither do you :-( .Next: #17.9: Late Imperial Rostra