London Eye
The London Eye was a giant Ferris wheel and a well-known landmark in London.
In the early morning of 1 January 2005, the newly regenerated Eleventh Doctor flew west over the Thames, past the Eye, whilst clinging by his fingers from his TARDIS' doorway, before climbing back aboard and being thrown nearly nine years back in time. (TV: The Eleventh Hour)
Three months later, in April, the Ninth Doctor and Rose Tyler discovered that the Nestene Consciousness used the landmark as a transmitter to activate its Autons as it was circular and that was what was needed to send the signal, and the pair shut down the Autons' operation. (TV: Rose)