I think that 1 does the best job of conveying massive size, but you might want to try swinging the camera up higher and zooming out a little bit, use atmospheric perspective to make the ground seem very far away, and clear that its the ground.
Perhaps put a building on top that is also clearly on the ground to further emphasize it. and if you have something that allows for movement up and down put that in there too.
But yeah, I think looking down on the world will have the best means of conveying raw size.