On Pokemon soul silver the cinnabar gym is located inside Seafoam Islands.
you have to get a key in the Pokemon mansion
in the bottom of the Pokemon mansion
i think top of Pokemon mansion
the pokemon gym is actually in seafoam islands, just surf to the right and enter the cave
it is in the basement in the Pokemon mantion.
The Pokemon Mansion is on Cinnabar Island, west (left) of the Pokemon Gym.
Defeat Gym Leader Blain on Cinnabar Island.
surf through passage ways in front of the island
It is in the Pokemon House (in the basement), left of Cinnabar Island.
Do you remember that first gym that was closed when you came to it the first time around? Fly to Viridian City and you will see that it is open. Defeat the Gym Leader and you can go to the Elite Four!
Seafoam Islands, They moved there instead of Cinnabar Island