Absolutely nothing - it is a very ordinary bridge. You may be thinking about Tower Bridge, which is the only bridge across the Thames that can be opened to allow ships with tall masts to pass underneath while people can still walk across the top of the bridge.
There aren't any. It's a very ordinary pre-stressed concrete bridge. Maybe you're thinking about Tower Bridge.
Tower Bridge has a unique design so is world famous'
No, it is a fully operational bridge used 24/7 by vehicles and pedestrians. It has been there since 1894 and is the only bridge in London that can open to let tall ships pass underneath. It is quite unique and therefore visited by many tourists every year as it is adjacent to the Tower of London. It is sometimes mistakenly called London Bridge by foreigners.
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.
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.
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.
London Bridge was falling down, so they made a song.
It isn't. Maybe you're confusing it with Tower Bridge.
No, but there is a museum at the bridge which has an admission charge.