In the cinnibar island gym.
its inside the mansion
The 7th leader is Blaine. He uses fire pokemon.
you go in the Pokemon mansion and the gyms key is some ware in there.
You have to find a key in the Pokemon mansion to open up the 7th gym. After you beat the 7th gym leader the 8th gym will open
Fire, so get out your Blastoise, Vaporeaon, Lapras, or Golduck.
It's locked. The key is located in Pokemon Mansion, which is just beside the Gym.
This TM is given to you by the 7th gym leader Blaine after defeating him.
go to cinnabar island then go into Pokemon mansion go through here to get the secret key which opens the 7th gym.
You need to go to the Pokemon mansion in Cinnabar Island. Go to the basement and obtain the Secret Key. Then go to the Pokemon Gym and it will be unlocked!
In his Gym in Cinnabar.