The International Congresses of Modern Architecture (CIAM) were organizations established in 1928 at Château de La Sarraz in Switzerland. In its declaration, CIAM defined the principles of functional urbanism, which were later elaborated during the fourth congress in Athens as follows: "Urbanism means organizing all the activities of life in general in cities and countries. It is not merely an aesthetic matter, but henceforth functional reasons must be considered the only effective factors in city-building matters. The most important subject in relation to cities is to organize the following activities systematically: a - Housing, b - Work, c - Recreation, sports, and entertainment." The declaration emphasized the importance of the land issue as follows: "The uncontrolled expansion of urban areas, resulting from various land transactions, land speculation, and inheritance laws, must be changed so that the land is governed and controlled publicly. This expansion and development can, at the first step, be accompanied by socializing the resources derived from the existing unjust surplus value." The declaration's authors rejected the academic spirit prevailing in urbanism and proposed a reform in the way architects are trained. According to them, "The academic spirit prevailing in the country forces enormous amounts to be spent on monumental buildings, thereby encouraging a kind of outdated luxury at the expense of ignoring more urgent and necessary goals in urbanism."

The second CIAM congress in Frankfurt in 1929 was devoted to the topic of minimum housing. A significant number of plans for small houses were presented in the publication at the end of the congress. These houses shared a common feature: the ground floor, where living space was prohibited, had a hygienic and functionally satisfactory area. The third congress in Brussels (1930) addressed the topic of "Logical Methods in Building Placement." The final report of this congress, which included critical views on this important subject, was prepared by prominent CIAM representatives such as Le Corbusier, Gropius, and others. The representatives fully examined the advantages and disadvantages of various types of buildings and categorized them into three grades. Among the articles submitted to the congress, many addressed the need for precise descriptions of housing types that are optimally equipped with shared services.

The primary topic of the fourth congress, held in 1933 on a passenger ship between Marseille and Athens, was functional cities. This congress concluded with a resolution known worldwide as the "Athens Charter." The congress presented research on the current state of cities, their uncontrolled and chaotic expansion, and the causes of existing problems. Additionally, it formulated a logical plan for urban design, enabling cities to optimally house the four vital functions: "Housing, work, recreation, and communication." This congress also recommended the preservation of architectural heritage, emphasized the necessity of a complete and analytical initial study for any urban design, and highlighted the importance of addressing specific urban issues within the framework of comprehensive plans that include the surrounding region.

Although it may seem surprising, upon studying the resolution of the fourth congress, despite the assumption that it should be one of the best references and documents in modern urbanism, some criticisms and issues arise. Notably, under the title "Athens Charter," three different reports exist with discrepancies in details.

The first report, published simultaneously in France and Greece at the end of 1933, comprises two parts: observations and resolutions (conclusions). It constitutes the main text, which has remained nearly unknown.

The text more widely recognized in Europe was published in 1943 by Le Corbusier on behalf of the French group participating in the conference. This version somewhat modified the original text and became known worldwide as the "Athens Charter." Le Corbusier divided the original text into paragraphs, added explanations, and subtly altered the meaning of the initial "observations."

Four years later, a book was published in the United States, authored by José Luis Sert. This book, a translation of the aforementioned "resolutions" into English, differs slightly from the original text. Although the changes in these two cases are minor, understanding the real value of CIAM's congresses requires returning to the original text published in 1933.

Presently, criticisms can be made about some points in the declaration. Nevertheless, it must be acknowledged that this declaration provided only a rough image of a kind of comprehensive composition of land and functional buildings for various purposes, not a city where the sole function is to accumulate a population with drastically different material and spiritual needs. The original text articulated the needs related to the four primary functions while ignoring other needs and issues.