Anyone with a tenuous knowledge of the Batman universe will know that Arkham Asylum is not the type of place you want to find yourself. It is home to Gotham’s criminally insane (i.e. Batman’s villains), and therefore a very, very unsafe place to be, and it's now being rumoured that Ben Affleck's Bruce Wayne could find himself locked up in the facility in his upcoming solo movie.
The anonymous sources behind the rumour stress that this is just a rumour and nothing has been confirmed as of yet, but we do know that Arkham already exists in the DC movie universe since it’s where the Suicide Squad will be rounded up later this year, and Affleck’s Batman is set to appear in that, so it stands to reason they’ll set up Bats’ incarceration in that Arkham-focused feature in order to gear us all up for the solo movie, and also to get arses in seats from the explosive word-of-mouth that would ensue.
Maybe there’s just one scene there, maybe the whole Film takes place there. The sources claim that if this rumour is true, the Caped Crusader will find himself an inmate at Arkham, but as it is just a rumour, it’s possible they’ve got their facts wrong and he’s just visiting someone, or maybe he’s there because the security couldn’t do their job (as they so rarely can) and there’s a riot on their hands that they need him to deal with. They could be making a film adaptation of Batman: Arkham Asylum (smart move: film adaptations of videogames always turn out great). There’s any number of possibilities for what this could entail. Maybe it’s just a rumour to throw people off and the film will really be set underwater or in outer space.
But maybe it’s not. If it’s true, why would Bats find himself behind Arkham’s bars? What reason does the city of Gotham have to put Batman in a mental asylum with all of his enemies? Gotham’s seedy political landscape full of shady, bribable politicians (with the exception of Harvey Dent, but then he became a supervillain so he doesn’t count) could have something to do with it, if they’re in cahoots with the bad guys – if they get Batman in Arkham, they have him right where they want him.
Or maybe a court of law just reached the verdict that he is criminally insane. He dresses up as a bat and kills people, for crying out loud. He’s nuts. But then Bruce Wayne would be outed as Batman, and it’s a little early in the franchise for that to happen.
There could be some truth to this rumour as it’s a piece that fits the same puzzle as another recent rumour about the film from another anonymous source (so totally reliable then).
It was indicated that Affleck’s Batman movie will be “crammed” with villains, featuring “most” of the Dark Knight’s established opponents (of which there are literally hundreds, by the way), and the only way for that to be possible and have the film be simultaneously under a day long, there would have to be at least a portion of the film set in Arkham Asylum.