Do you know Big Ben? Big Ben is not the name of a man. It's the name of a big clock in London. This clock has four faces. So, no matter which direction( 方向) you stand in, you can read the time on the face of Big Ben. The minute hand on each face is about four metres long. If you go to London, you may want to visit the Houses of Parliament(国会大厦). In that place, you will find Big Ben sits at the top of the clock tower. You will probably hear it and see it. The big clock makes such a loud sound. It strikes every quarter of an hour. Big Ben has been the most famous symbol of London.