The City of London has a peculiar conical structure, known locally as "cucumber". Just as the new CCTV building in Beijing is called "big pants", the original official name of "small cucumber" is the Swiss Reinsurance Headquarters Building, up to 180 meters, which is the most expensive office building in Britain. Cucumber is known as London's first ecological skyscraper. Its shape is based on the principle of aerodynamics, so that under the building there will be no strong gust like other high-rise buildings; glass curtain wall allows sunlight into the room as far as possible to achieve natural lighting; good ventilation design reduces the use of air conditioning.