Go to Route 214 (the path connecting Veilstone to Pastoria), and on the right side of the path, a new area should’ve opened up called Spring Path. Follow the path to Sendoff Spring then go all the way to the back. Use Rock Climb to slide down the mountain. There you will see a cave—Turnback Cave. It’s a labrynth there so make sure you have some Escape Ropes in your inventory or a pokemon that knows Dig.
you find turn back cave in dimond on route 214
turn back cave
girantina is in that cave at lv 70
turn back cave
in turn back cave
you get pass turn back cave
turn back cave
turn back cave.
The turn back cave in Pokemon Platinum is in Seodoff Spring near veilstone city
after you got the national pokedex there will be a new lake cooled turn back cave near route 214.
In Turnback cave on Pokemon Patinum there is a portal to the Reverse World.
Pokemon 487 is giratina and you can find it in turn back cave
go to turn back cave