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 tower in which Big Ben is located is officially called the Elizabeth Tower; originally just the Clock Tower, it was renamed in 2012 for the Diamond Jubilee of Elizabeth II.
The tower was designed by Augustus Pugin in a neo-gothic style. When completed in 1859, it was, says horologist Ian Westworth, "the prince of timekeepers: the biggest, most accurate four-faced striking and chiming clock in the world". It stands 315 feet tall, and the climb from ground level to the belfry is 334 steps. Its base is square, measuring 39 feet on each side. Dials of the clock are 23 feet in diameter. On 31 May 2009, celebrations were held to mark the tower's 150th anniversary.
Big Ben is the largest of five bells and weighs 13 ¹⁄₂ long tons. It was the largest bell in the United Kingdom for 23 years. The origin of the bell's nickname is open to question; it may be named after Sir Benjamin Hall, who oversaw its installation, or boxing heavyweight champion Benjamin Caunt.