No where but in PEARL you can catch a BAGON route 210 with a pokeradar.
No where
go to route 210 from Nathan
you can't catch a salamence in Pokemon diamond but you can migrate one from a game boy advance game of Pokemon or use an ar and use the catch trainer's Pokemon cheat and find somebody with a salamence then get one
migrate. totally migrate.
once you have national pokedex talk to dawns sister everyday and shell say there is a wild outbreak.
you have to catch a bagon then evolve to shelgon then evolve to salamence
There's a small room that opens up after you beat the elite 4. It will have a TM on the land and a 25% chance to find a bagon. Level it to 50 and it evolves into a salamence.
Migrate it from LeafGreen, FireRed, Ruby, Sapphire, or Emerald
no where
Elite Four Drake (Dragon-type user) has a Salamence.
If you're looking for a Salamence in Diamond, unfortunately you aren't going to find one. Bagon, the original form of Salamence, is only found in Pearl and Platinum. You can find Bagon on Route 210 in Diamond/Platinum with the PokeRadar. If you're playing Pearl, you'll have to trade it from either of those games, or from RSE.
I know you cant catch a Bagon in Diamond cuz i wanted one to evolve it into Salamence and foud out that they arent even in Diamond