Batman Arkham City fansite – ArkhamCity has a rather interesting interview with Rocksteady Studios, developer of Batman: Arkham Asylum and the soon to be released Arkham City. One of the things they talked about was Arkham City’s massive terrain compared to Arkham Asylum and how the Batman will be “held back” in exploring the City right off the uh, bat.
“You’ll be able to explore most of the city right from the start," game director Sefton Hill said, "we really wanted to keep the player in-powered as Batman and didn't want to put any artificial barriers in there to stop him getting around."
"There are areas that you’ll uncover obviously as you play through the game, there’s lots of secrets and rewards as you play through the game and new areas you get to explore." Hill continued. "But you can go and explore the main city right from the start, if you do explore it right from the start you’re going to find lots of secrets around the place and different things to see. We worked really hard to try and tell the story of the different sections within Arkham City. "
He also talked about certain areas being controlled by gangs that you may find too challenging as you progress through the story, naturally limiting how much you'll want to explore.
That’s certainly food for thought. If you ever read the comics, looks like Arkham City will be borrowing a few elements from the “No Man’s Land”story arch - with each gang/villain having their own section of the City