Justice League: A Better World
Gotham City is a large metropolitan city located in New Jersey. It is famously home to Batman and Robin, as well as many other heroes and villains. It was founded as a port town in the 17th Century. They are also protected by the Gotham City Police Department, who work hard to deal with the city’s disproportionate amount of costumed criminals. There have been many different Mayors of Gotham City, as they tend to have a high mortality rate.
In 1996 an underground atomic explosion under Wayne Manor destroyed the Batcave. The place complete states are still under quarantine even when mayor radiation protocols have been used to clean the place. ( Radiation Level: 4 )
DC HEROES RPG 3rd Edition p.151
DC Wikia entry