Last summer, I had a tour to see the famous Big Ben, the bell inside the tower. Originally, the clock tower was named St. Stephen's Tower, but its name was changed to Elizabeth Tower last year in honour of the queen for her Diamond Jubilee. (A tower in the Houses of Parliament is named Victoria Tower, named after the Queen Victoria in her Diamond Jubilee as well.)
Big Ben (Elizabeth Tower) before our tour
We arrived in the building across the street to begin our tour; access to Elizabeth Tower can be reached from a tunnel underground that connects the buildings with Parliament. We could not take photographs on the tour, but we climbed over 300 steps to the top. We stopped off at a couple of times. On the way up, we stopped off to have a look at the clock and bell mechanism and watched this when the clock struck a quarter to. We saw how the mechanism worked and saw old pennies on the weights to counter-act the machinery so that it keeps accurate time as changes in weather can affect it. We also saw the weights counter-act to ring the bells above.
Our last stop was to see Big Ben (the bell). The bell was cast at the same place as the American Liberty Bell (Whitechapel Bell Foundry). We listened to the bells and watched them as the struck on the hour. We saw the crack in the bell and the portcullis symbol engraved on it. There were excellent views over London from here.
On the way down, we walked around (behind) the clockface and were told about how the clockface was cleaned and about the gas lamps (now electric lamps) that used to light up the clockface.
To view a virtual tour of Big Ben, see: http://www.parliament.uk/visiting/online-tours/virtualtours/bigben-tour/ To view photographs of the inside of the tower, see: http://www.flickr.com/photos/uk_parliament/sets/72157615971627846/