Central London is the innermost part of London, UK. There is no official definition of its area but its characteristics are understood to include a high density built environment. The Palace of Westminster is the meeting place of the House of Commons and the House of Lords, the two houses of the Parliament of the United Kingdom. Commonly known as the Houses of Parliament after its occupants, the Palace lies on the north bank of the River Thames in the City of Westminster, in central London. The London Eye is a giant Ferris wheel on the South Bank of the River Thames in London. Also known as the Millennium Wheel. The structure is 443 feet (135 m) tall and the wheel has a diameter of 394 feet (120 m). When erected in 1999 it was the world's tallest Ferris wheel.