you go through it to find the key to the gym
Cinnabar island.
there is no cinnabar island in sapphire. cinnabar is on firered and leafgreen. also in Pokemon yellow special pikachu edition ^_^ don't forget that dude...
You can go from Fuscia City through the Seafoam Islands and surf to Cinnabar Island. Or you can go to Pallet Town and surf south to Cinnabar Island.
Cinnabar mansion
cinnabar island
in the bottom of the Pokemon mansion
It's hinted that Mewtwo is responsible for it; when he got out of control, the mansion was almost destroyed by his power.
it is in the basement in the Pokemon mantion.
Revive the fossil from the scientist in Cinnabar Island.
his old gym burned in lava now he is in seafoam island which is directly east from cinnabar
You must continue going to the far right of cinnabar while surfing into a cave, there you will have to search and then youl find a key there
You can catch a Growlith in the Pokemon Mansion on Cinnabar Island.