From Bulbapedia, the community-driven Pokémon encyclopedia.
A Contest Hall is where Pokémon Contests and Pokémon Super Contests are held.
In the Hoenn Contest Halls, there is one reception counter (two in the Lilycove contest hall) and Berry Blenders for making Pokéblocks. There are also photo frames for the winning Pokémon.
In the Sinnoh Contest Hall, two additional reception counters can be found: one for linked Super Contests, and the other for practice sessions. The Berry Blenders are gone, as Pokéblocks are replaced by Poffins.
Contest Hall locations
Super Contest Hall locations