As you approach Rockettower Plaza you'll see a large sphere perched on a marble stand. The sphere is supported by a thin film of water, allowing you to spin the sphere in its base. The sphere itself is so heavy that the fountain of water supporting it would shoot 210 feet in the air if the sphere were removed.
Sometimes the fountain may be turned off due to drought conditions, but you can still examine the sphere for some surprises (see if you can find Cinderella's Castle!).