thats easy u go to palifilog town and go east then u will see a path

take a mach bike then surf to pacific log until you see a opening. Go in the opening and tou will see land. Go up. When you arrive in the sky pillar take your bike and ride as fast as you can on the broken ground. continue doing that until you see raquaza

you must take elite four (league) then go to paifidlog and surf to the right and then you will see two or something rocks that has opened (after the pokemon league)