Pewter City Gym
Brock is the leader of the Pewter City Gym. The trainers located in the gym use rock type Pokemon. All Pokemon games where the player is in the Kanto Region have the Pewter City gym, but the look of the gym varies slightly through each generation of the games. When the player defeats Brock they will receive the Boulder Badge which allows the holder to use Flash outside of battle.
Cerulean City Gym
Misty is the leader of the Cerulean City Gym. The trainers located in this gym use water type Pokemon primarily. The look of the gym varies slightly in each game, but it always looks like a swimming pool. When Misty is defeated the player will receive the Cascade Badge which allows the holder to use Cut outside of battle and allow Pokemon up to level 30 obey.
Vermilion City Gym
The Vermilion City Gym is lead by Lt. Surge. Electric type Pokemon are the favorite of the trainers located in this gym. In all Kanto region games, the Vermilion Gym appears in almost exactly the same way with only visual upgrades. In each game there are fifteen trash cans lined up in the room and the player must find two switches, if they fail to find the second switch directly after the first then the switches will reset. In the Generation II games, the traps are not on. When Lt. Surge is defeated the player will receive the Thunder Badge which will allow Fly outside of battle.
Celadon City Gym
The Celadon City Gym is lead by Erika. In this gym it is grass type Pokemon that are preferred by the trainers in it. While the visual style of the gym varies between generations, it is always full of plants and trees like a greenhouse. Players who defeat the gym leader Erika will receive the Rainbow Badge which will allow the player to use Strength outside of battle and allow Pokemon up to level 50 obey.
Fuchsia City Gym
Fuchsia City Gym is a little different than the other gyms in the Kanto Region. In the generation 1 and 3 games the gym leader is Koga, while in the generation 2 and 4 games the gym leader is Janine. In all of the games the gym looks like a dojo and has invisible walls that the player must navigate. Poison is the primary type of Pokemon in this gym. When either Koga or Janine is defeated the Soul Badge will be awarded which will allow the use of Surf outside of battle.
Saffron City Gym
The Saffron City Gym is lead by Sabrina. Psychic is the primary type of Pokemon in this gym. In order to get to the gym leader in the Saffron Gym a maze of nine rooms with teleporters must be navigated. In generations 1 and 3 there are trainers to battle in seven of these rooms while in generations 2 and 4 there are only four rooms in which to battle trainers. When Sabrina has been defeated the Marsh Badge will be awarded which allows the use of Rock Smash to be used outside of battle and allow Pokemon up to level 70 to obey.
Cinnabar Island Gym
Cinnabar Island Gym is led by Blaine. In generations 1 and 3 the gym is located on Cinnabar Island, however in generations 2 and 4 the gym is located on the Seafoam Islands. The reason for the change is that in the Gen 2 and 4 versions Blaine's gym was destroyed by an erupting volcano, forcing him to move the gym. Fire type is the preferred type of Pokemon in all versions of Blaine's gym. Once Blaine has been defeated the Volcano Badge will be received which allows the use of the Waterfall HM.
Viridian City Gym
The Viridian City Gym is led by Giovanni in generations 1 and 3, but led by Blue in generations 2 and 4. In all versions of the game except for generation 2 games, the gym floor has the auto moving arrow tiles on the floor in which the player must navigate through to get to the gym leader. The Pokemon type of choice in this gym is ground type. Once either Giovanni or Blue has been defeated, the Earth Badge will be awarded and will allow the use of Rock Climb and any Pokemon of any level will obey.