a very large structure, in the shape of a dome (= a building with a round roof) that was built near Greenwich, an area of south London. It cost £700 million to build and was designed by Richard Rogers, a well-known British architect. It was open to the public in the year 2000 with an exhibition on various subjects, for example, work, travel, religion, money, the environment and life in Britain. Some people thought that it cost too much and that there were more important projects to spend such a large amount of money on. The Dome is now owned by a private company. It is called the O2 and contains the O2 Arena, which is used for concerts, etc.