Pokémon Ruby and Sapphire/Ever Grande City 2

The top part of Ever Grande City includes the Pokémon League and the largest Pokémon center in the game. Two Cool Trainers block the way to the league, they will only let you pass once you show them your eight badges.

Pokémon Center
The center is the same as any other but supersized, it even has its own PokéMart. Make sure you get all the Pokémon you want to use for the league and heal them. The PokéMart (on the right side) sells full heals, full restores, hyper potions, max potions, max repel, revive, and ultra balls.