The World of the Future Fair was a theme park located at Gotham City.
During its initial days, the Fair was an amusement park very visited by the population of Gotham City. Bruce Wayne visited the park along with his girlfriend Andrea Beaumont. They really enjoyed the experience, and in the park, Bruce watched a futuristic car that would serve him as inspiration for the Batmobile.
After it closed down and became derelict, the Joker used this theme park as hideout. Salvatore Valestra visited this park to ask help to Joker, but he instead killed him with his toxin and dynamited his penthouse. Later, the Phantasm visited the Joker to kill him. Batman foiled the attempt, but the Fair exploded because Joker had rigged the complex. All three survived the destruction.
The World of the Future Fair was inspired by the 1964 New York World's Fair. Furthermore, the song "Welcome to the Future" is similar to "There's a Great Big Beautiful Tomorrow", the song played in the Disney/General Electric sponsored "Progressland".