There's a new informant system which provides you with a few interesting spots to aim for on your vast map. That's if you can keep a specific assailant conscious until the end of one of the game's many fights, in order to interrogate him once you've dealt with everybody else. Tricky stuff.
As a collectathon it all seems admirably restrained, however. Rocksteady admits that throwing in dozens of tokens and doo-dads to chase after might be fun, but it would hardly make you feel like Batman, who's not known for his predilection to leave a crime-scene and go treasure hunting. So the main game is still designed to keep you moving through it with a vigilante's sense of purpose.
One section sees Batman storming the courthouse where Two-Face is making a play for power by putting Catwoman on trial. It showcases the way that the narrative blends exploration and fighting fairly seamlessly.
The game full of loving touches, of course - Two-Face's hang-out has exactly half it's facade dishevelled, for example, while street signs around the neighbourhood are filled with smart references for the hard-core fans.
But there's also a real ease in the way Rocksteady guides you from staking out a building's entrance to heading inside and planning your way through a huge rumble. The battles themselves are massive - a brawl with Two-Face's goons features at least 20 different lackeys to pummel.
While new moves such as double-punches and an added emphasis on using Batman's gadgets mean it's easy to get lost within the rhythm of combat, you still need to be tactical.
Scanning the crowd before wading in is essential and it pays to deal with armed targets first - preferably using new stealth takedowns, such as the ability to punch straight through flimsy walls or knock two unwitting goons' heads together. Armoured enemies, meanwhile, will only succumb to the new beat down manoeuvre that sees you unleashing a flurry of blows with a glorious burst of button mashing.
Plenty of other ideas have been tweaked to make sense of the shift in scale. Batman's Cryptographic Sequencer - originally just a fancy key for getting through fancy doors - now allows you to hack into distant radio chatter to get a better idea of what's going on across town.
Smart gadgetry inside your headpiece will automatically amplify any conversations going on nearby, which should help a lot when you're down on the narrow streets with poor visibility.
Rocksteady's also promising to rebalance Detective Mode, making sure it's a tool rather than an exploit you won't want to turn off. This time, you may actually get to see some of the art design as you move through the game.
Alongside Two-Face, Catwoman and the ailing Joker, the developer's slowly unveiling a range of new baddies, hinting at famous faces who are yet to be revealed while finding the room to tease die-hards with appealingly obscure additions.
Remember Calendar Man? He popped up in just two or three stories, if memory serves, but he's back in Arkham City offering a weird and murderous twist on Animal Crossing. He'll apparently spout different dialogue depending on whether you're playing the game on Valentine's Day, say, or New Year's Eve.
That kind of detail, alongside the obvious care with which this big, atmospheric game is being put together, provides another indication of how seriously Rocksteady takes its role as the Dark Knight's caretaker. If you played Arkham Asylum and thought it was too brilliant a trick to pull off twice, the joke might just be on you.