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 FireRed and LeafGreen Versions - Bulbapedia, the community

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Altering Cave - Pokémon FireRed #49

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

Altering Cave - Pokémon FireRed #49

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

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

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

Pokemon FireRed/LeafGreen Walkthrough - PokeDream