you must go 2 spear piller eith azure Flute use the flute and stairs will apear walk up until u meet arzas
hall of origins
beat the Pokemon league
There is no such thing as a main hall.
Hall Matron Argenta
There is no Contest Hall in Pokemon Black because Pokemon Black does not have Pokemon Contests. Instead of Pokemon Contests, Pokemon Black has Pokemon Musicals. Pokemon Musicals are held in the Pokemon Musical Building in Nimbasa City.
You have to beat the Pokemon League.
the cave of origins you need to battle 1000 Pokemon and10 Pokemon trainers
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The Super Contest hall
The Hall Of Origin
pokecommunity
After beating the Pokémon League, your rival will escort you to the Hall of Fame.