The tower was designed by Augustus Pugin in a neo-Gothic style. When completed in 1859, its clock was the largest and most accurate four-faced striking and chiming clock in the world. The tower stands 315 feet (96 m) tall, and the climb from ground level to the belfry is 334 steps. Its base is square, measuring 39 feet (12 m) on each side. Dials of the clock are 23 feet (7. 0 m) in diameter. On 31 May 2009, celebrations were held to mark the tower's 150th anniversary.