Gotham City

From the Lego Batman Wiki

Gotham City is a large city and home to Batman and several supervillains. It contains many famous locations such as Arkham Asylum, Gotham City Hall, and Wayne Manor. It has been the main site of almost every Batman comic, movie, television show, etc. The game will most likely take place only within Gotham City. It is also likely that the game will occur in the sewers and waterways of Gotham with Killer Croc as a character/enemy.