Possibly the most famous clock face and chimes in the world, Big Ben is actually the name of the biggest bell (13.5 tons) inside The Clock Tower (320ft) which forms part of the HOUSES OF PARLIAMENT.
The clock's four dials each have a diameter of 23ft, the minute hands are 14ft long and the numerals on each face are nearly 2 feet high. The accuracy of the clock movement is controlled by the placing of old pennies in the mechanism.
There is a light at the top of the tower which, when lit, indicates that the House of Commons is sitting. During the day you can tell if they're sitting by looking for a flag at the top of the nearby Victoria Tower which is the tallest and largest of the Westminster towers.
The tower which houses Big Ben has been called by many names, one of the most popular being St Stephen's Tower. However, the official line, from the Head of Public Information at the Palace is that the Clock Tower is simply called The Clock Tower. The subject of John Buchan's "39 Steps", the Clock Tower is unfortunately not open to the public so you won't be able to check how many steps actually lead to the belfry.