767. Norman Foster, City Hall,

London, 1998-2002 (United Kingdom)

Located near Tower Bridge, London’s new City Hall—actually the headquarters of the Greater London Authority—has given the capital a bold new landmark that speaks about the pressing need to respond to environmental concerns. Displaying no discrete façades, only a continuous rounded surface clad in glass, the form of the building was designed to reduce surface area and thus to improve energy efficiency. The modified sphere, 45 metres tall, leans back toward the south, thus minimising its exposure to direct sunlight. By means of ‘green’ technology the building is said to consume only a quarter of the energy of a conventional office building: roof vents are controlled by weather sensors, solar panels are used to generate energy, and it is naturally ventilated by operable windows in all offices. The heat produced by computers and lights is recycled. Inside, a 500-metre-long helical walkway rises the full height of the building; recalling the ramp of the Guggenheim Museum, it is more closely related to a similar feature in Foster’s Berlin Reichstag. At the base of the spiral is a multi-use debating chamber with viewing gallery. Security concerns have unfortunately precluded access to the interior for regular visitors.