Milˌlennium ˈDome, the BrE AmE
a large building in Greenwich, London, built by the UK government to contain a big public ↑ exhibition celebrating the start of the new ↑ millennium in 2000. It stayed open for a year and after a long period of being unused, the inside of the Dome was rebuilt. In 2005 it was given a new name The O2, and became an entertainment centre.