The London Eye, or the Millennium Wheel, is a cantilevered observation wheel on the South Bank of the River Thames in London. It is Europe's tallest cantilevered observation wheel, and the most popular paid tourist attraction in the United Kingdom with over three million visitors annually. It has made many appearances in popular culture.

A Ferris wheel is an amusement ride consisting of a rotating upright wheel with multiple passenger-carrying components 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 cars are often referred to as capsules or pods.