CIAM (Congrès Internationaux d'Architecture Moderne) was founded in Switzerland in 1928 to lift modern architecture from the level of individual buildings into a social programme. The Weissenhof exhibition of 1927 had shown that this circle could establish a shared language; the congresses carried that language from housing standards to the scale of the city.

The fourth congress, in 1933, met aboard a ship sailing from Marseille to Athens and compared analyses of thirty-three cities. Its conclusions were formulated in the Athens Charter that Le Corbusier published in 1943: the city should be divided into four functions that do not mix; dwellings should sit in tall blocks within green space; traffic should be separated from pedestrians; historic fabric should be kept only where it has monumental value. The street — for centuries both the city's circulation and its place of encounter — was deliberately abandoned.

The doctrine's force came from meeting the urgency of post-war reconstruction. The ruined cities of Europe, the mass housing programmes of the Soviet bloc, new capitals such as Brasília and the post-1960 development plans of many countries, Turkey among them, all used the same scheme. Millions of people gained sanitary housing for the first time through this programme — the part most criticism forgets. But separating functions produced single-use, car-dependent environments with weak public life. In the 1960s Jane Jacobs defended the street itself, and Team 10 attacked the scheme from inside CIAM; the organisation dissolved in 1959, and the argument continues as the founding tension of urban design today.