[2][3] The style is characterized by modular and rectilinear forms, flat surfaces devoid of ornamentation and decoration, open and airy interiors that blend with the exterior, and the use of glass, steel, and concrete.

Nevertheless, these same qualities provoked negative reactions against the style as monotonous, austere, and incongruent with existing landscapes; these critiques are conveyed through various movements such as postmodernism, new classical architecture, and deconstructivism.

[15] However, International Style architecture demonstrates a unity of approach and general principles: lightweight structures, skeletal frames, new materials, a modular system, an open plan, and the use of simple geometric shapes.

Hitchcock and Johnson's 1932 MoMA exhibition catalog identified three principles of the style: volume of internal space (as opposed to mass and solidity), flexibility and regularity (liberation from classical symmetry).

[17] Common characteristics of the International Style include: a radical simplification of form, a rejection of superfluous ornamentation, bold repetition and embracement of sleek glass, steel and efficient concrete as preferred materials.

[17] Further, the transparency of buildings, construction (called the honest expression of structure), and acceptance of industrialized mass-production techniques contributed to the international style's design philosophy.

The ideals of the style are commonly summed up in three slogans: ornament is a crime, truth to materials, form follows function; and Le Corbusier's description: "A house is a machine to live in".

The style is characterized by an emphasis on volume over mass, the use of lightweight, mass-produced, industrial materials, rejection of all ornament and colour, repetitive modular forms, and the use of flat surfaces, typically alternating with areas of glass.

[16] Around the start of the 20th century, a number of architects around the world began developing new architectural solutions to integrate traditional precedents with new social demands and technological possibilities.

The work of Victor Horta and Henry van de Velde in Brussels, Antoni Gaudí in Barcelona, Otto Wagner in Vienna and Charles Rennie Mackintosh in Glasgow, among many others, can be seen as a common struggle between old and new.

The International Style can be traced to buildings designed by a small group of modernists, the major figures of which include Ludwig Mies van der Rohe, Jacobus Oud, Le Corbusier, Richard Neutra and Philip Johnson.

[24] The Gropius-designed Bauhaus school building in Dessau, built 1925–26 and the Harvard Graduate Center (Cambridge, Massachusetts; 1949–50) also known as the Gropius Complex, exhibit clean lines[25] and a "concern for uncluttered interior spaces".

[30] The "International Style", as defined by Hitchcock and Johnson, had developed in 1920s Western Europe, shaped by the activities of the Dutch De Stijl movement, Le Corbusier, and the Deutscher Werkbund and the Bauhaus.

In the largest exhibition space, Room C, were works by Le Corbusier, Ludwig Mies van der Rohe, J. J. P. Oud and Frank Lloyd Wright (including a project for a house on the Mesa in Denver, 1932).

In 1922, the competition for the Tribune Tower and its famous second-place entry by Eliel Saarinen gave some indication of what was to come, though these works would not have been accepted by Hitchcock and Johnson as representing the "International Style".

However, American anti-Communist politics after the war and Philip Johnson's influential rejection of functionalism have tended to mask the fact that many of the important architects, including contributors to the original Weissenhof project, fled to the Soviet Union.

Bruno Taut, Mart Stam, the second Bauhaus director Hannes Meyer, Ernst May and other important figures of the International Style went to the Soviet Union in 1930 to undertake huge, ambitious, idealistic urban planning projects, building entire cities from scratch.

[42] A large proportion of the buildings built in the International Style can be found in the area planned by Patrick Geddes, north of Tel Aviv's main historical commercial center.

Encompassing more than 500 buildings, most of them designed by Edvin Engström, it remains the largest coherent functionalist or "International Style" villa area in Sweden and possibly the world, still well-preserved more than a half-century after its construction in 1933–40 and protected as a national cultural heritage.

When Walter Gropius and Marcel Breuer fled Germany they both arrived at the Harvard Graduate School of Design, in an excellent position to extend their influence and promote the Bauhaus as the primary source of architectural modernism.

After World War II, the International Style matured; Hellmuth, Obata & Kassabaum (later renamed HOK) and Skidmore, Owings & Merrill (SOM) perfected the corporate practice, and it became the dominant approach for decades in the US and Canada.

[citation needed] In June 2007 UNESCO proclaimed Ciudad Universitaria of the Universidad Nacional Autónoma de México (UNAM), in Mexico City, a World Heritage Site due to its relevance and contribution in terms of international style movement.

Other notable Mexican architects of the International Style or modern period are Carlos Obregón Santacilia, Augusto H. Alvarez, Mario Pani, Federico Mariscal [es], Vladimir Kaspé, Enrique del Moral, Juan Sordo Madaleno, Max Cetto, among many others.

Jakarta, Indonesia In 1930, Frank Lloyd Wright wrote: "Human houses should not be like boxes, blazing in the sun, nor should we outrage the Machine by trying to make dwelling-places too complementary to Machinery.

"[50] In Elizabeth Gordon's well-known 1953 essay, "The Threat to the Next America", she criticized the style as non-practical, citing many instances where "glass houses" are too hot in summer and too cold in winter, empty, take away private space, lack beauty and generally are not livable.