Unova Pokémon League is a new stage introduced in Super Smash Bros. for Nintendo 3DS, it's based on Pokémon Black and White.
The stage have two floating platforms, N's Castle also appears in the background, a stairway extends from it, changing the stage, sometimes Reshiram, Zekrom, Shaymin, Whimsicott or Milotic will appear on the stage, causing a effect, when Zekrom appears, it will let the stage inclined.
In Pokémon Black and White, Unova Pokémon League is the location of the region's Elite Four, who may only be challenged after defeating all eight Unova Gym Leaders. It is located on a large hill north of Victory Road and it requires traveling through a mountain to reach the entrance.
N's Castle is owned by the mysterious N. Zekrom or Reshiram can be caught here, depending on the game, as well as being Team Plasma's supreme headquarters.