You have to go to the Pokemon mansion, This mansion is located in thee same town as the 7th gym leader. In the Pokemon mansion there will be many ways to walkthrough. (Hint, The mewtwo statues have switches.)
After obtaining the other 7 badges you return to Viridian City and the gym will be open.
go to cinnabar island then go into Pokemon mansion go through here to get the secret key which opens the 7th gym.
Get the key from the basement of the mansion next to the gym.
In Pokemon FireRed and LeafGreen you can't open a gym.
If you mean, "how do I unlock the Gym where he is", you have to go into the mansion and get to the basement. There you will find the key to open the Gym
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.
u have to find the key in the Pokemon mansion i think
after u beat the gym leader on cynabar Island the gym, that wuz closed the whole time will be open
Because the key to open the door is hidden in the Pokemon Mansion.
You must beat the seven gym leaders, the elite four, and your rival. Then you have to capture 60 Pokemon to get your Rainbow pass the will allow you to travel to Island 7 in Pokemon FireRed.
It is atchrily the 8th gym. It will open when you get the first 7 gym badges