In Canalave city.
you need to dfeat the 4th gym leader
The 6th gym leader is in Fortree City.
The 6th gym leader is in Canalave City.
The Gym leader Fantina has it
fatina (hearthome)
The 6th Gym Leader in Pearl is Byron who is in Canalave City.
The 6th gym is in Saffron City the gym leader is Sabrina she uses Psychic type pokemon.
The 6th gym leader in Pokémon Sapphire is found at the Fortree Gym. The name of the gym leader here is Winona.
steel
Byron
sixth gym laeder
gem leader blue