Gym Leader Castle
A Gym Leader Castle is a location in the Pokémon Stadium series where players may battle the Gym Leaders and the Elite Four of the Pokémon games of that Generation.
The first Gym Leader Castle was simple: It was a darkened, curving path leading from spire to spire, with each spire's top in the shape of that Gym Leader's Badge. To advance to the next spire, players would need to defeat each of Kanto's Gym Leaders in turn, eventually making way to the Elite Four and Champion, their rival.
The second Gym Leader Castle was more complex. Instead of it being an actual castle, it featured differently-designed rooms for each of Johto's Gym Leaders, each one representing the leader's type in its design. Like its predecessor, players would need to defeat each of Johto's Gym Leaders in turn, eventually making their way to the Elite Four and its Champion, Lance.
After the defeat of Lance, however, like in Gold, Silver, and Crystal, players may challenge a revamped version of the Kanto Gym Leader Castle. Though it has the same battle arenas as the first game, the outside design is slightly different, as now, instead, the eight badges of Kanto are on the sides of the castle's spires, and the eight are arranged more closely together. After the defeat of Kanto's set of eight, trainers unlock the battle with Red, who, unlike his Game Boy Color counterpart, does not have a team that one would see in Pokémon Yellow.