It's located in the basement of the mansion.
Go into the Pokemon mansion and look around. At the end you will find the key to the door.
The secret key is in the Pokemon mansion (Cinnabar Island) in the basement.
You will find it in the Pokemon mansion on cinnabar island.
That key unlocks the door to the cinnibar island gym.
You will find the key to the Gym of Cinnabar Island, From the Pokemon Mansion that is on the same island.
you have to find it inside the Pokemon mansion located on cinnabar island
With the secret key which is found in the Pokemon mansion.
Find the key in the pokemon mansion on the same island.
its in the Pokemon mansion behind the lab on cinnibar island
It's in Cinnabar island. It's where you get the key to open the Gym #7
On cinnabar island but you need to get the secret key in Pokemon mansion first.
bottom floor of Pokemon Mansion