The Babel mode lets you take on randomized stages either by yourself or with a friend. You can only unlock these stages by earn Gold Prizes in the Golden Playhouse.

Stage	How to unlock
Altar	Earn one Gold Prize from the Golden Playhouse on Normal difficulty or higher.
Axismundi	Earn nine Gold Prizes from the Golden Playhouse on Normal difficulty or higher.
Menhir	Earn three Gold Prizes from the Golden Playhouse on Normal difficulty or higher.
Obelisk	Earn five Gold Prizes from the Golden Playhouse on Normal difficulty or higher.