Did you mean Cinebar Island? If so it is in the mansion
In the basement of the Pokemon mansion on cinnaber.
go to pallet town and swim down to cinabar island and get the key in the mansion and go the gym and unlock the door and there you go
How do you unlock the door in the old man's house who lives on mossdeep city on Pokemon Ruby
You can find the key to unlock the door in Pokemon mansion
At cinnabar island at the pokemon lab third door.
You walk up to the door and use cut.
In the toliet
In the basement of the Pokemon mansion on cinnaber.
You have to get the key to the gym in Pokemon Mansion, but after you unlock the entrance, he is already inside there, so it's assumed that he's already in there even before you unlock the entrance.
go to pallet town and swim down to cinabar island and get the key in the mansion and go the gym and unlock the door and there you go
You have to have the member's pass. You go in, and you fall asleep, waking up on New Moon Island, where you can catch Darkrai.
you have to use cut on the door. but it doesn't work if you just click on the dotted door as if you were cutting a tree go into the start menu then Pokemon then select one of them that knows cut
How do you unlock the door in the old man's house who lives on mossdeep city on Pokemon Ruby
The key is in the Pokemon mansion.
I think with cut!!!
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.
You can find the key to unlock the door in Pokemon mansion