In 1893 up-and-coming engineer George Washington Gale Ferris Jr. created an attraction for the world's fair in Chicago: A giant, steam-powered wheel on which passengers could gently ride to a height of 250 feet for a spectacular view. These days, Ferris Wheels (or observation wheels) are all the rage. Correspondent Roxana Saberi spins the story of their origins, and takes a ride on some of the most notable Ferris wheels around.