I believe that One Piece’s moon is in fact in geostationary orbit, exhibiting it’s entire gravitational force over a single point. Reverse mountain. This is the biggest contributing factor in the phenomenon of upward flowing water, and also explains why the rest of the world isn’t affected by regular tidal forces. But why is this relevant? First we’re gonna need some locations for the map points:
Aside from excellent foreshadowing on the part of Oda this flag is also a vital clue. The World Government are aware of the road poneglyphs and Raftel, but are unable to reach it. The fact that they have been unable to reach it, even long before the beginning of the great pirate era and the rise of the Yonkou suggests that the poneglyphs were given to their enemies. So they likely also point to the nations of their enemies.
One poneglyph on Zou, an independent nation isolated from humans. One in possession of Kaido, likely found in Wano, who are still independent of the World Government. Many have speculated that the unknown poneglyph is from Elbaf but I believe the Elbaf poneglyph is the one owned by Big Mom. The final poneglyph rests on the moon, and will be brought back by Eneru
Now let’s complete the map. But first, take a look at this:
One thing is evident from this picture. There are many island combinations that take 2 from each half of the grand line or one from each of the 4 blues which lead to reverse mountain being the intersection point. Reverse mountain is commonly theorised to be the location of Raftel. Statistically speaking, it’s the location at the end of the grand line which is most likely to be the solution on a 2D map. But surely this makes it too easy? The solution can’t be something so simple as to be reached by anyone with a bit of basic logic?
And so we return to the moon. Instead of thinking of the map in 2 dimensions, try thinking of it in 3, with the moon as one of the points. Now lets take 2 nations from opposite sides of the grand line. Alabasta, who whilst being members of the World Government were likely allies of the AK given their refusal to move to Mariejois and ownership of a poneglyph, and either Wano or Baltigo, as both are likely roughly the right distance into the New World for this to work and aren’t WG islands. And finally, the reason for the theory of the geostationary moon, the final point is Fishman Island. Connect the dots in 3 dimensions on a globe. The line between Alabasta and Wano/ Baltigo cuts through the globe, meeting the line between the moon and Fishman Island at a point just beneath reverse mountain.
Raftel is likely deep under water or underground, in what is essentially the exact opposite position to Fishman Island which rests 10,000 meters below sea level beneath Mariejois on the opposite side of the world.