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 usually extended to refer to both the clock and the clock tower. The official name of the tower in which Big Ben is located was originally the Clock Tower, but it was renamed Elizabeth Tower in 2012 to mark the Diamond Jubilee of Elizabeth II. When the tower was completed in 1859, its clock was the largest and most accurate four-faced striking and chiming clock in the world. The tower stands 96 m (315 feet) tall, and the climb from ground level to the belfry is 334 steps. Dials of the clock are 7 m (23 feet) in diameter.