Since it was officially opened on New Year's Eve 1999 (as part of the millennial celebrations), the London Eye has become one of London's most popular attractions. It has 32 sealed 'pod' capsules, fitting a total of 800 people, revolving on a huge Ferris wheel. One go-around takes half an hour with the wheel rotating at only twice the speed of a tortoise sprinting, so you can step on and off without the wheel needing to stop!
The London Eye is the fourth-tallest structure in London, so the far-reaching views over London are spectacular. On a clear day you can see as far as Windsor Castle. And the slow speed of the rotation means there's plenty of time to see everything and take lots of photos.