The United States pavilion's designers choose a Buckminster Fuller dome, two hundred feet high (20 stories) and 250 feet in diameter. As in all of Fuller's domes both little and big, they used three- dimensional units, a triangle on the outside, hexagonal on the inside, and curved to fit a given arc, as its structural basis. By connecting them together in the shape of a dome, it distributed the structure's weight over the whole surface. To avoid his usual half-dome that produced a squat look, the pavilion's designers built a beautifully proportioned, three-quarter sphere that fit the site ideally. It was the most complicated of his domes. It used an elaborate system of retractable shading screens to control the heat within. A computer adjusted the screens in accordance with the sun's rays. Its exterior covering was exquisitely tinted, and surprisingly it was lovely to look at.excerpted from a paper describing the Architecture of Expo 67
http://www.biosphere.ec.gc.ca/The_Sphere/Richard_Buckminster_Fuller-WS30956246-1_En.htm
