As you already know this is the original Julius Caesar Rostra and then Augustus enlarged it. So let's just stick to Julius Caesar's small Rostra, as shown in this photo. You can see the remains of the marble steps on the left side that once covered the entire back and the curve of this staircase. Not much room on top as you can see, as I said before this was more of a speaker's platform like the original in the Comitium. Also that cornice work has been placed on top in modern times, it was once mounted in front. Picture Caesar's open coffin carried up and placed in the middle and then Marc Antony climbing the stairs and giving his famous speech. And of course all of the other Emperors walking up those steps to speak to the crowds from the Augustus Rostra.
Behind the Rostra they found in the nineteenth Century excavations five bases for columns.
These were also excavated again in 1959. It's a fact that five columns with statues on top were put up by Emperor Diocletian 303 AD.
The columns were between 30-35 feet and the middle one was the tallest with a Jupiter statue on top.
But who knows perhaps there were column/statues there before? And his just happened to be recorded in history perhaps replacements after the 283 Fire? It wouldn't be the first time a later Emperor gets credit unintentionally for something built earlier. But anyway, these five column/statues are always shown as being mounted *on* the Rostra in modern reconstruction drawings.
But it is very doubtful.
First off the weight would be too much for the Rostra floor (base, 10 m column and statue).
Second they found five bases right there.
Third a relief on the Arch of Constantine, photographed here, really seems to show the column/statues behind the Rostra.
These column bases are still buried beneath the street paving you are walking on. By the way, those paving stones are modern, they were put in in 2005.Next: #11.5: Milliarium Aureum