Big Ben

You've most likely heard of Big Ben, an icon of England and London. It's often thought to be seen in pictures of London, movies that involve the city, and on calendars. It's even more notable that the 30 St Mary Axe, and has been in London far longer. What you may not know is that Big Ben is not the name for the tower: it's the name of the bell for the clock, and it's inside the tower.

That's right: the tower, which itself is really the icon that everyone is familiar with, is actually called the "Clock Tower". The bell inside is what is called "Big Ben"; however, due to the misunderstanding being widespread, when people refer to "Big Ben" they almost always mean the entire tower, rather than the bell. Don't worry...I also didn't know about the bell, until my parents told me about it.

This link and this one have more information about Big Ben and the Clock Tower.