You must fight your way through Pokemon mantion, the top left building of the island. The key is at the end of the possible path, good luck.
in the bottom of the Pokemon mansion
it is in the basement in the Pokemon mantion.
there is a key in the Pokemon mansion... you need it to get into the gym... search the Pokemon mansion thoroughly
if you got it from the Pokemon mansion it opens the cinabar Pokemon gym
You will find the key to the Gym of Cinnabar Island, From the Pokemon Mansion that is on the same island.
its inside the mansion
In the game Pokemon Yellow you have to beat the leader of gym seven in order to win the Volcano Badge. The leader of this gym is named Blaine and he specializes in fire type Pokemon. To enter this gym you first have to get the secret key. This key is located in the building across from the lab.
you go in the Pokemon mansion and the gyms key is some ware in there.
at the basement of the Pokemon mansion there is a 'secret key' and that opens up the 7th gym.
There is a key in Pokemon Mansion (Searching for Mew there on LeafGreen. I know a glitch to get Mew before Misty on Pokemon Yellow without GAMESHARK!) You have to hit the switch on every Statue (At least in LeafGreen. I beat it!) and that Item You NEED to get is the gym's key. Get it. Go to the gym. Use it. Your in. Pokeglitch20
to open the door of the 7th gym!
You can find the key to unlock the door in Pokemon mansion