We know very little about the Old Kingdom, but we think we can paint a picture of it from what we know. For starters, the closest approximation you can get to the idea looks like this:
It looks like an ancient Greek/Roman city, the pillars are an obvious sign, and it’s honestly a bit suspicious that we’re being given such a teaser when very little in the series has anything to do with Greece/La Ancient Rome, but those who have one speak volumes.
For starters, we have the ancient weapons, Poseidon, Uranus and Pluto, which are respectively named after a Greek god, a Greek titan and a Roman god. We have the Lunarias, specifically King, who appears to have a tattoo inspired by a laurel wreath.
Finally, the Old Kingdom and the Romans share similar histories. They were once the seat of a huge empire that controlled and influenced the world, and then they fell into disrepair, paving the way for the world we know today. Rome also had a history of slavery, and we know that slavery already existed in the ancient kingdom.
So it seems that the Old Kingdom has a strong Greek/Latin influence and that the Ancient Kingdom itself was the equivalent of Rome in One Piece, just as Dressrosa is the equivalent of Spain, Wano is Japan, and Alabasta is Egypt. We know that the name of the kingdom has to be a recognizable word or name in the show, otherwise they wouldn’t have killed Clover for almost revealing it, because the word itself is objectionable to the world government.
We think we can figure out the name of the ancient kingdom, because it’s a word that itself is a major theme in the series, and which literally comes from the word “Rome”.
The Old Kingdom of Romance, or The Dawn of Romance
We believe that the name of the Ancient Kingdom is the name given to us in the first chapter of the series, and was almost the name of the series itself before Oda called it “One Piece”. Romance comes from the Latin Romanicus “in the manner of the Romans”, from Romanus “Roman”.
We know that the word “Dawn” is already an important aspect of the seriesit is an event that people are waiting for, and in cases like Pedro and Kiku, they are ready to give their lives for it.
Ultimately, it’s still a pirate story, so if the ancient kingdom’s name and design may come from Roman influence, we believe its story will be more grounded in history/ pirate mythology. Specifically, the lost pirate city of Libertalia.
Libertalia was a legendary free colony founded by pirates, where people of all colors, creeds and convictions were free from scrutiny. Sounds familiar to you, because it looks like much to what Luffy’s journey itself is building, and what the government itself has worked so hard to prevent.
We believe Old Kingdom, Romance, was just thata tribe where people of all races could one day come together and share drinks and sake like brothers, waiting for the day when the promise of their kingdom would be fulfilled, waiting for the day called…… The Dawn of romance.