Disney Fact #6

Florida law states that any building 200 ft or higher must be topped by a blinking red  light to warn pilots of it's presence at night. Believing that the light would ruin the magic if placed atop the Cinderella Castle, the imagineers had to find a way to make the building look larger than it actually is. 

Each 'layer' of the Cinderalla Castle is scaled smaller than the previous which makes each story appear further away from the guest, and hence taller, than it actually is. The entire castle, standing just under the requirement at 189 ft, is one big optical illusion!