When Walt Disney secured his Central Florida location for Walt Disney World, he won numerous concessions from government, but none so far-reaching as the "Reedy Creek Improvement District" (RCID). The RCID is the name for the territory that Walt Disney World occupies, and it is a uniquely autonomous zone, which hardly has to answer to the state government at all. The zone can build its own nukes, run its own building codes, and generally do whatever it likes. This comprehensive Wikipedia entry on RCID is nothing short of fascinating.
The Improvement District has far-reaching powers. Through the District, the Walt Disney Company could construct almost anything within its borders, including a nuclear power plant (which it never built, opting instead for a more traditional plant that supplements power from outside the District). The District, as with any municipal corporation, can issue tax-free bonds for internal improvements. This became a point of contention when a 1985 law limited the amount of tax-free bonds in Florida. The eligible bonds were chosen randomly, causing the District to beat out Orange County, which had planned to build low-income housing, in 1989. In addition to the power of eminent domain outside the District, the one other power that the District was given that it would not have had if it were simply the two Cities was the power to ignore any laws, including state laws, about zoning and land use. When the state later established the Development of Regional Impact study process, the Walt Disney Company, through the District, was able to avoid the paperwork and streamline the process to build theme parks and other attractions. On the other hand, county taxes, including property and sales taxes, still apply within the District.
The planned residential areas never came (though part of the plans for EPCOT did come through), due in part to the fear of losing control of the District, causing some to cry foul. Most notably, Richard Fogelsong argues in his book, Married to the Mouse: Walt Disney World and Orlando, that the Walt Disney Company has abused its powers by remaining in complete control of the District. On a related note, the Disney-controlled town of Celebration, Florida, which was built with many of Walt Disney's original ideas, which have evolved into a form of New Urbanism, was deannexed from the City of Bay Lake and the District to keep its residents from having power over the Walt Disney Company. Celebration lies on unincorporated land within Osceola County, with a thin strip of still-incorporated land separating it from the rest of the county. This strip of land contains canals and other land used by the District.
(via The Disney Blog)