Trafalgar Square, London, UK.
There is a plinth at each of the four corners of the square. The two southern plinths carry sculptures of Henry Havelock and Charles James Napier. The northern plinths are larger than those as they were designed to have equestrian statues, and indeed the northeastern plinth has one of George IV. The fourth plinth on the northwest corner, designed by Sir Charles Barry and built in 1841, was intended to hold an equestrian statue of William IV, but remained empty due to insufficient funds. For over 150 years there was much squabbling about what to do with the plinth, but very little agreement, until 1999, when a sequence of three contemporary artworks that would be displayed on the plinth was announced. The success of this initiative led to a commission being formed to decide on a use for the plinth. Eventually that commission unanimously decided to continue using it for the temporary display of artworks (from Wikipedia).