Batman: Arkham Asylum certainly didn't short change players when it came to hidden collectibles, offering Riddler trophies, interview tapes and plenty more to chip away at your free time.
Well, it turns out there's one more secret that players didn't discover: Warden Quincy Sharp's secret room.
Inside this area you'll find blueprints which layout Arkham City, a clear nod to next year's highly anticipated sequel.
The room isn't located on any of the maps, so you'll likely need a bit of help finding it. Good job then that GameInformer has posted a video guide.