From Bulbapedia, the community-driven Pokémon encyclopedia.
The Challenge Hall (Japanese: チャレンジホール Challenge Hall) is a location found in Pokémon Trading Card Game and its sequel, Pokémon Card GB2: Here Comes Team GR!. Tournaments are regularly held in Challenge Hall, in which winners are awarded with rare promotional cards.
When a player enters the Challenge Hall, they are brought on stage and seated at a table. There, players will be challenged by three random opponents (the third of which is always Ronald) with random decks.