Its in Pewter city.
Brock's gym is in Pewter City.
where can i find the second gym in Pokemon platinum
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in his gym
In her Gym
In the gym!
In the goldenrod gym.
You will find the key to the Gym of Cinnabar Island, From the Pokemon Mansion that is on the same island.
Find the secret key in the Pokemon Mansion,( Next to the gym)
TM80 Rock slide is found inside mt. Coronet, but the only way to find it is to use the poketch radar.
You find him in the last Gym in Sootoolis City.He is the last Gym leader
You can find the 2nd gym in the south part of Eterna City.