Location from pokemon-kanto by
Brock's Rock-type gym at the edge of Pewter City — Kanto's first gym and the one that teaches most trainers what type disadvantage actually feels like.
Pewter Gym awards the Boulder Badge. Its Rock-type Pokémon — Geodude, Onix — are brutal for unprepared Electric- and Normal-type teams. Ash lost here in his first attempt: Pikachu's Thunderbolt passed harmlessly through Onix, and he had to forfeit. He won the rematch after Brock himself, on his way to resigning the gym leader role in favor of his father, coached Ash in exploiting the gym's sprinkler system — wetting Onix's rock body so Pikachu's electricity could finally conduct.
A squat grey stone building with a large boulder-shaped door. Inside, the battle arena is a rocky field with boulders strewn across it, dusty air, spotlights fixed on the trainer platform. A set of stone bleachers for spectators.