Absolutely nothing. It is a very ordinary modern (1973) bridge.
The middle of the bridge opens to let boats pass
The original bridge was built by the Romans about 50ad. At the time, it was the only bridge crossing the Thames in London so it just became known as London Bridge.
Grand Canyon, London Bridge and Hoover Dam.
London Bridge is a very ordinary bridge which crosses the river Thames in London. The first bridge across the river was built by the Romans about 2000 years ago and there has been a bridge on the site ever since. At one time there were shops and houses on the bridge, which eventually collapsed - hence the children's song 'London Bridge is Falling Down'. Many foreigners mistakenly think that Tower Bridge - the next bridge downstream and much more interesting - is London Bridge.
It is a concrete bridge so has no need to expand.
The London Bridge in Arizona was designed by John Rennie and dates from1830 so could be described as an historic monument. The current London Bridge in London England only dates from 1973 so is hardly historic.
Waterloo Bridge is part of central London so you will have to be more specific.
There isn't another bridge anywhere else in the world that looks anything like Tower Bridge so it is instantly recognisable. It is the only bridge over the river Thames that can be raised to allow tall-masted boats to pass under it. It is still possible for pedestrians to cross the bridge, even when it is 'open' to allow a boat to pass underneath.
Because the original bridge was the ONLY bridge in London at that time.
The London Bridge in London isn't popular with tourists. It's a very ordinary bridge used by thousands of commuters every day to get to work. The London Bridge at Lake Havasu City in Arizona is also a very ordinary bridge which was built in London in 1820 and rebuilt in Arizona in 1973.
Tower Bridge and London Bridge.
It isn't. Maybe you're confusing it with Tower Bridge.