Altering Cave - Pokemon Fire Red and Leaf Green Guide - IGN

Found north of Sixth Island, this cave only have Zubats. However, if you have an E-reader connected to a gameboy advance using Japanese E-reader cards

Pokemon Colosseum - cube - Walkthrough and Guide - Page 6 - GameSpy

Let's Play Pokemon Fire Red Part 83: Outcast Island/Altering Cave

Celadon City - Pokemon Fire Red and Leaf Green Guide - IGN

Pokémon FireRed and LeafGreen/Rock Tunnel — StrategyWiki

Pokémon FireRed and LeafGreen/Six Island — StrategyWiki

Pokemon FireRed and LeafGreen :: Full Walkthrough

Altering Cave - Pokémon FireRed #49

Altering Cave - Bulbapedia, the community-driven Pokémon encyclopedia

Altering Cave - Pokémon FireRed #49

Lavender Town - Pokemon Fire Red and Leaf Green Guide - IGN