The sixth gym is in Canalave City of Pokemon Pearl, west of Jubilife City.
The first gym in Pokemon diamond is in Oreburgh City
you go to the lake to battle team galatic and then you go to snowpoint city to get your seventh badge.
The sixth gym is in Fuschia City, where you fight Koga, Poison type leader.
The sixth gym badge (the Marsh badge) is located at Saffron City's gym. It is in Gym Leader Sabrina's possession, so you have to defeat her to obtain it.
fire and ground
One of your Pokemon has to learn surf.
Byron in Canalave City is the sixth gym leader in Pokemon Diamond. He specializes steel-type. His 3 pokemons are Bronzor, Steelix, and Bastiodon.
bryron and his pokemons are brozor, stelix and bastiodon.
byron the sixth gym leader u fight him in canalave gym
Your friend doesn't have a dad in the game, but Roark does (first gym battle). His name is Byron (sixth gym battle)
After you beat the sixth gym leader, you are allowed to use strength which moves the boulders.
The Canalave City Gym is the 6th gym. To get there, you must Surf west from Jubilife City. Get HM03 Surf in Celestic Town.
you go to heartom city and meet fantina in the gym PS you have to go on the elevator up
The sixth gym AKA the fortree city gym specializes in Flying Type Pokemon.
The Fortree gym.
you need to use a strong fighting type like a lucario or medicham