Big Ben (Clock Tower) late at night, Westminster, London

Big Ben late at night, Westminster, London, originally uploaded by Craig Grobler.

The Clock Tower is the world's largest four-faced, chiming clock. The structure is situated at the north-eastern end of the Houses of Parliament in Westminster, London. It is often colloquially referred to as Big Ben, which is actually the nickname of the main bell housed within the tower (formally known as the Great Bell).The Clock Tower has also been referred to as The Tower of Big Ben and, incorrectly, St Stephen's Tower, which is actually the spired tower towards the middle of the Palace and is also the main point of entry for attendees of debates and committees.