According to Tamago, there are a total of thirty Poneglyphs in the world. Each Historical Poneglyph tells a piece of history long forgotten. The four Road Poneglyphs each identify a location which form a map leading to the final island in the Grand Line, Laugh Tale. Kaido is in possession of a Road Poneglyph, and this Road Poneglyph is currently in Wano. But where is its exact location?
On Skypiea, it was said that Seastones, as well as Sky islands are created from a certain substance called “Pyrobloin”, and that this substance is ejected into the air by volcanoes. And it’s a fact that Wano is the country where Seastone originated from.
Wano has one of the active volcanoes in the middle of the country, the Mt. Fuji, which is obviously direct reference to the active volcano of Mt. Fuji in Japan. We know the fact that Poneglyphs were created in Wano Country, so it’s a fair assumption that Poneglyphs also contains “Pyrobloin”.
As the guy on Skypiea described, when Pyrobloin gets in contact with water in the air, the Sky islands are formed, which are very soft. Pyrobloin is also used in creation of Seastones, which is most likely mixed with something else, which makes it extremely tough (described to be tough as the diamond), but Pyrobloin was also used to create something indestructible, Pyrobloin mixed with some other specific substance gave the Poneglyph, but the recipe for that was lost.
You can see volcanic ash and red coloring, as if its inside the volcano, and it makes sense. You create them at the place with the most concentration of Pyrobloin.
So, Pyrobloin is extremely versatile substance, you can make soft stuff, hard as the diamond stuff, and indestructible stuff depending on what you’re mixing it with, and Vegapunk has been experimenting on it for a long time, who knows what kind of weapons (SSG?) he has made using Pyrobloin.
This could explain why the World Government wants to get a hold of Wano. Not only would they not have to get Pyrobloin and Seastone from the Black Market(Kaido) anymore, but they could have unlimited free Pyrobloin, and they could also profit a lot and become even stronger in the process.
Where is the Road Poneglyph?
The one place we have not yet explored in Wano, and the one we’re getting closer to.
The Road Poneglyph has been in the same place where its been for the past 800 years, the place where it was created at. In Zou, the Road Poneglyph was inside giant Elephant, in Wano it will be inside giant volcano, on Elbaf it could be inside that giant tree (Yggdrasil presumably).
What if Luffy punches Kaido inside Mt Fuji, and once inside it, they find the Road Poneglyph?
Theory by BuggyDClown (https://www.reddit.com/user/RoronoaLuffyZoro)