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 often extended to refer to the clock or the clock tower as well. Big Ben is the largest four-faced chiming clock and the third-tallest free-standing clock tower in the world. It celebrated its 150th anniversary in May 2009 (the clock itself first ticking on 31 May 1859). The design for the Clock Tower was English architect Augustus Pugin's last before his final descent into madness and death.