14 Mind-Blowing Batman: Arkham Series Facts
13. The Plans For Arkham City Were Always Hidden In Asylum
Although many developers patch content in and out of their games, Rocksteady actually already had the idea for Arkham City when they were building Asylum - electing to place some blueprints behind a hidden explodable wall that led to Warden Sharp's office.
It would mark a tradition for the studio, as Scarecrow's mask is discoverable on a small boat offshore in City, thereby hinting at his return as the main villain in Arkham Knight.