i think top of Pokemon mansion
On Pokemon soul silver the cinnabar gym is located inside Seafoam Islands.
you have to get a key in the Pokemon mansion
Blue is on Cinnabar Island. But to be able to fight him, you must find Blaine the old Cinnabar gym leader. He is in the seafoam islands. Beat him, and then talk to Blue again. He will then return to his gym, where you can fight him!
the pokemon gym is actually in seafoam islands, just surf to the right and enter the cave
The sixteenth gym leader, Blue, should be in Viridan City. To get him to appear in his gym, defeat Blaine in Seafoam Islands (Cinnabar Island's volcano erupted). Then, visit Cinnabar Island to see Blue standing there. After talking to him, he should be at the gym then.
Blue is in Cinnabar Island. But to be able o fight him, you have to find Blaine, the gym leader. He is in the Seafoam Islands. Beat him and then talk to Blue again. H will then return to his gym.
Blaine is located East of Cinnabar Island, his gym is where the Seafoam islands used to be. I think you have to talk to Gary/Blue on Cinnabar Island while you're there to face him later as well.
With the secret key which is found in the Pokemon mansion.
Talk to Blue on Cinnabar Island.
meet blue, the gymleader on cinnabar island
Cinnabar Island.
surf through passage ways in front of the island