There are 24 bridges across the Thames in London; the first one was built by the Romans between the City of London and Southwark. It was wooden and there were many vaiations on it, which burned down, collapsed and slid into the mud. There is some evidence that this is the basis for the nursery rhyme, London Bridge is Falling Down.
A stone bridge was built in 1176 and was lined with shops - the most famous bridge in the country at the time. Fires, floods and other natural and non-natural disasters all took their toll and many bridges were built on this site. In 1973 the present London Bridge was erected. It looks like this:
As part of the lead-up to the Olympics, the ring logo has appeared on Tower Bridge, one bridge downstream from London Bridge. Tower Bridge was built between 1886-94 and looks like this:
London Bridge was bought by an American in 1967 and rebuilt in Lake Havasu City, Arizona. Both the buyer and the vendor vehemently deny the popular rumour that he actually thought he was buying Tower Bridge. The mistake is common, but no less annoying for all that.