Aerial view of the Millennium Dome structure with masts and roof structuure in place.

The Millennium Dome in the United Kingdom is an engineering marvel and the world's largest single roofed structure It is one of the most easily recognised and controversial landmarks in London and is a deceptivily simple tensioned cable net structure similiar to a suspension bridge with a roof of weather resistant plastic The millennium celebrations held in the Dome were widely considered to have been a disappointment and the building was closed for some time It was purchased by the Anchultz Entertainment Group and is being transformed into a vast 20, 000 seat indoor venue The World Gymnastics Championships will take place in the Dome in 2009 and it will be converted into a multi-purpose sport and entertainment arena before the Olympic Games in 2012 and will continue to host major events after the Olympics.