Big Ben is the nickname for the great bell of the clock at the north end of the Palace of Westminster in London,and is generally extended to refer to the clock or the clock tower as well, It is the largest four-faced chiming clock and the third-tallest free-standing clock tower in the world. It celebrated its 150th anniversary on 31 May 2009, during which celebratory events took place.The erecting of the tower was completed on 10 April 1858. The clock tower has become one of the most prominent symbols of both London and England, often in the establishing shot of films set in the city.
The clock dials are big enough that the Clock Tower was once the largest four-faced clock in the world.
The clock and dials were designed by Augustus Pugin. The clock dials are set in an iron frame 7 metres (23 ft) in diameter, supporting 312 pieces of opal glass, rather like a stained-glass window. Some of the glass pieces may be removed for inspection of the hands. The surround of the dials is gilded.