A Ferris wheel (sometimes called a big wheel, observation wheel, or, in the case of the very tallest examples, giant wheel) is a nonbuilding structure consisting of a rotating upright wheel with multiple passenger-carrying components (commonly referred to as passenger cars, cabins, tubs, capsules, , or pods) attached to the rim in such a way that as the wheel turns, they are kept upright, usually by gravity.
Some of the largest modern Ferris wheels have cars mounted on the outside of the rim, with electric motors to independently rotate each car to keep it upright. These wheels are sometimes referred to as observation wheels and their cars referred to as capsules, however these alternative names are also used for wheels with conventional gravity-oriented cars.
The original Ferris Wheel was designed and constructed by George Washington Gale Ferris Jr. as a landmark for the 1893 World's Columbian Exposition in Chicago. The generic term Ferris wheel is now used for all such structures, which have become the most common type of amusement ride at state fairs in the United States.
Since the original 1893 Chicago Ferris wheel there have been nine world's tallest-ever Ferris wheels. The current record holder is the 167.6-metre (550 ft) High Roller in Las Vegas, US, which opened to the public in March 2014.
"Pleasure wheels", whose passengers rode in chairs suspended from large wooden rings turned by strong men, may have originated in 17th-century Bulgaria.
The travels of Peter Mundy in Europe and Asia, 1608–1667 describes and illustrates "severall Sorts of Swinginge used in their Publique rejoyceings att their Feast of Biram" on 17 May 1620 at Philippopolis in the Ottoman Balkans. Among means "lesse dangerous and troublesome" was one:
...like a Craine wheele att Customhowse Key and turned in that Manner, whereon Children sitt on little seats hunge round about in severall parts thereof, And though it turne right upp and downe, and that the Children are sometymes on the upper part of the wheele, and sometymes on the lower, yett they alwaies sitt upright.