Mt. Chimney

Mt. Chimney is a Volcano. Team Magma or Team Aqua can be found here (or both in Pokémon Emerald). Later on when Maxie/Archie is defeated, trainers enter this location waiting for challengers to challenge them to a battle.

Team Magma
Magma Admin Tabitha:

Magma Leader Maxie:

Team Aqua
Aqua Admin Matt:

Aqua Leader Archie:

Emerald
Double Battle:

Magma Admin Tabitha: Magma Leader Maxie: