This is a design for City Hall, the headquarters of the Greater London Authority, built between 1998 and 2002 by the British architects Foster and Partners. The design brief was to achieve a low-energy building. In this drawing from 1999 the architects detail passive energy-saving techniques such as openable windows, circulation of fresh air, photovoltaic panels that harvest energy from the sun, and the use of boreholes to draw up cold groundwater to help cool the building. Their intention that the building should use only 25 per cent of the energy one would expect for a building of this size is printed under the title. The drawing was made using Computer Aided Design (CAD) and this kind of view is known as a section. It is not the kind of seductive image intended to impress a client or to wow the public. Instead it is a means of communicating design information through simple graphics, and in this it is very successful. The Victoria and Albert Museum holds several similar drawings from the same scheme, each one dealing with a different design issue.