So as we all know that the four place in the road poneglyphs supposed to intersect at the location of Raftel. But the world of One Piece is a ball, which mean the four points will intersect twice. The second time at the exact opposite side of the world.
Besides that there is the famouse theory that says that Raftel is inside the Reverse Mountain(you can see it here). If that theory is true it means that the exact opposite side of the world is Mariejois. If all of this true, it means that the second intersect leads to the treasure Doflamingo talked about.