In the house you jerk!
u can find it in Pokemon mansion.
u have to find the key in the Pokemon mansion i think
its inside the mansion
The Pokemon that can be found in the Pokemon Mansion in Pokemon FireRed are Rattata, Raticate, Grimer, Muk, Growlithe, Koffing, Weezing and Ditto and you will also be able to find the key that will unlock the door to the Cinnabar Gym.
the secret key is in the Pokemon mansion - Celadon city basement
you go in the Pokemon mansion and the gyms key is some ware in there.
The basement.
You get the card key which lets you open the gym which is locked.
You get the card key which lets you open the gym which is locked.
Get the key from the basement of the mansion next to the gym.
You go to cinnabar island then go inside the Pokemon mansion. Press A at every pokeball u find.
I believe it is on Cinnabar Island. To enter the gym, you have to get through the Pokemon Mansion and find the secret key.