The Thames Barrier is the first crossing as the river is entered from the estuary. Although not a bridge, when raised if forms a total block to the incoming tide. It was completed in October 1982 in order to protect London from the effects of high tidal surges due to certain weather conditions in the North Sea and has been raised at least 100 times since then. In this picture can also bee seen the Millennium Dome whish was built to celebrate the millennium. It has had a somewhat chequered history since then but is now the O2 entertainment arena. The surrounding area of the Isle of Dogs was once part of the very busy London Docks but since the containerisation of most cargo the business has moved to other deeper ports such as Felixstowe on the East Coast and Dockland has become a popular residential area for city workers.