Well, challenges and minigames. Batman: Arkham Asylum had that feature after you completed the story, and Arkham City incorporates challenges as an endgame.
According to G4TV writer Kevin Kelly, one of the challenges is a race, ”Moving on to the final challenge, Catwoman and Batman both raced from one point in the city to another, although Dax underscored the fact that this is not a mode in the game. Although after watching it, I sure wish it was. Both of them had to move through the city as quickly as they could, finally getting to the top of a Ferris wheel on the edge of the city. This is where Batman pulls ahead, showing off his new Grapple Boost ability that allows him to use the Grapple Gun while gliding to give himself a boost up and over obstacles.”
Batman: Arkham City will be released on PC, Xbox 360 and PlayStation 3 on October 18 in the US, October 21 everywhere else.