Designed by Joseph Paxton for the Great Exhibition of 1851 in London, the Crystal Palace showed for the first time, at large scale, that a building could be manufactured in a factory and assembled on site. Paxton was not an architect but a gardener and greenhouse builder; he drew his design from the glass-and-iron logic he had learned in the greenhouse.

The building's secret is modulation. The whole rests on a dimensional grid set by the size of a standard glass pane (about 1.2 metres); cast-iron columns, beams, and glass panels were mass-produced in the factory as multiples of this single module, carried by rail, and bolted in place. The result was that some 92,000 square metres of covered space were erected in only nine months — a speed unthinkable in a stone building. When the exhibition ended, the building was dismantled and rebuilt at Sydenham; demountability was part of the design.

The cast-iron frame carries the load; there is no such thing as a wall, only a glass envelope. This produces a volume that fills the interior with daylight and looks almost weightless — a transparency shocking to its contemporaries. The Crystal Palace thus unites prefabrication, modular coordination, and the glass-and-frame envelope to herald modern industrial architecture — from factories to skyscraper curtain walls.