Where Do You Go After Getting The 7th Gym Badge In Pokemon Platinum?

From the gym go down, down the stairs, go left keep going until you see a signpost to the right of it there is some rocks up the wall press a and it will say ......will a pokemons move scale it use rockclimb press yes go left you will see the blond guy and he will lead you to battle some galactics

You have to go to Veilstone City and you have to talk to the Grunt from the Galactic Team... Then you have to beat the Galactic Team.... Hope it helped! :D

First you go to Oberburg city then you find a cave you remember, then you use surf to get to the other side that you saw. Use rock climb to go up some stairs. You will need to use strength to get to a broken door of some sight. Then the police man you know will give you the black flute. Thats what I all know. But after you beat the elite four, go to celestic town, go to the brown house, talk to the old lady and the go back to spear pillar. You will see two Lev. 70 pokemon then. ( Dialga and Palkia). Dialga is in the blue portal and Palkia is the pink one. After you battle Dialga, go out then back in to battle Palkia. Hope that helps:)

Go to mt. Coronet then find giratina