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

Pokémon Emerald Version - Bulbapedia, the community-driven Pokémon

My take on Cerulean City for my edit of Leaf Green. Feedback

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

Pokémon FireRed and LeafGreen/Six Island — StrategyWiki

Seafoam Islands - Pokemon Fire Red and Leaf Green Guide - IGN

Pokémon FireRed and LeafGreen/Cerulean Cave — StrategyWiki

PK3/WC3: Unreleased Altering Cave Pokémon - Unreleased/Beta PKM

One Island - Pokemon Fire Red and Leaf Green Guide - IGN

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