Step on the portals until you get to the gym leader.
Saffron city.
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.
The sixth gym leader,Sabrina, is in Saffron City.
In the Kanto region, the sixth gym is in Saffron City. The gym leader is Sabrina.
Sabrina's gym in saffron city
The Sixth Gym leader is Chuck, he has a Hiryama and a Poliwrath.
One of your Pokemon has to learn surf.
shoot him with a non-existent rail-gun
Mt. Ember for the Ruby, and Sixth Isle for the Sapphire. Trade
in canalava city
Ummm... Which Pokemon game?
you stop playing Pokemon and get a life