Ludwig Mies van der Rohe's Barcelona Pavilion brings modern architecture's ideal of the 'free plan' to an absolute purity. There is no functional programme here — the pavilion was built only to represent a state at a world's fair, that is, as pure architectural expression. This lack of programme lets Mies show his idea of space in its most distilled form.

Mies sharply separates the bearing from the dividing. The roof is carried by slender, chrome-clad steel columns set in a grid. Because the walls now carry no load, they need not enclose space either: Mies places them as independent, free planes wherever he likes beneath the roof. Some walls extend outside, some stop short within; none closes a 'room'. The result is a space in which inside and outside, one area and the next, are not separated by sharp boundaries and through which the visitor flows continuously — what Mies called 'universal space' (a universal, flowing space).

Material here is the only ornament: polished green marble, travertine, grey glass, and chrome steel define the space with their own textures and reflections; there is no added decoration. Mies's principle of 'less is more' finds its most concrete expression — simplicity is not poverty but the flawless choice and proportion of every element. With its load-bearing frame, free plan, and pure use of material, the Barcelona Pavilion is the icon that set the standard for the glass-and-steel modernism of the following half-century.