The London Eye is a cantilevered observation wheel...

The London Eye is a cantilevered observation wheel on the South Bank of the River Thames in London. It is Europe's tallest cantilevered observation wheel, is the most popular paid tourist attraction in the United Kingdom with over 3.75 million visitors annually, and has made many appearances in popular culture.
The wheel's 32 sealed and air-conditioned ovoidal passenger capsules, are attached to the external circumference of the wheel and rotated by electric motors. Each of the 10-tonne capsules represents one of the London Boroughs, and holds up to 25 people, who are free to walk around inside the capsule, though seating is provided. The wheel rotates at 26 cm (10 in) per second (about 0.9 kph or 0.6 mph) so that one revolution takes about 30 minutes. It does not usually stop to take on passengers; the rotation rate is slow enough to allow passengers to walk on and off the moving capsules at ground level. It is, however, stopped to allow disabled or elderly passengers time to embark and disembark safely.
The London Eye is a very popular attraction. The London Eye opening times vary throughout the year, typically the attraction opens at 10:00 and closes between 18:00-20:30, better to check their website for exact timings on the day you intend to visit. You can save up to 15% when you book in advance online which is highly recommended as there queues to buy tickets on the spot can be really long.