Cinnabar Island

Cinnabar Island is a large island located off the southern coast of the Kanto region, south of Pallet Town. It is home to a large volcano. Blaine is the Gym Leader specializing in Fire-type Pokémon located inside of an erupted volcano. The island is connected to the mainland by two water routes: Route 20 in the east and Route 21 in the north, leading to Fuchsia City and Pallet Town, respectively.

Pokemon Mansion
The Pokémon Mansion is a decrepit, burned-down mansion on Cinnabar Island. It got its name because a famous Pokémon Researcher once lived there. Many burglars come to the mansion, trying to steal valuable items that may have been lost in the wreckage, challenging the player to a battle when spotted. Amongst the rubble and wreckage is information that the scientists who once worked there obtained a Mew and impregnated it with the genetically altered Mewtwo, who destroyed the mansion in its escape.

Volcano
Sometime after Red's journey through Kanto, a volcano emerged upon Cinnabar Island and erupted. The resulting eruption destroyed the entire island. Soon after, the island was rebuilt and the civilization somewhat returned. A Pokemart was built on the volcano while the gym was built inside of it.

Cinnabar Gym
The Cinnabar Gym is the official Gym of Cinnabar Island, it is based on Fire-type Pokémon and the Gym Leader is Blaine. Trainers who defeat him receive the Volcano Badge. Fittingly, it is built inside of the volcano on the island. The Cinnabar Gym is a fun affair featuring a series of multiple door like caves. Trivia questions about various Pokémon must be answered to move on. If the player correctly answers the trivia question, they are able to move on through the gym. However, when the player fails to answer a trivia question correctly, a battle with either a Firebreather or Super Nerd results, an alternative to unsealing the doors.