Humankind's enduring love for animals is the inspiration for WDW's fourth theme park, Disney's Animal Kingdom. At 500 acres and five times the size of the Magic Kingdom, Animal Kingdom is the largest in area of all Disney theme parks worldwide. The space gives Disney Imagineers plenty of scope for their creativity, and it allows for growth, an example of which is Expedition Everest. Opened in 2006, it's the park's biggest thrill attraction -- a runaway train ride on a rugged mountain complete with icy ledges, dark caves, and a yeti legend.