As a prominent distinctive subdiscipline, intellectual history has been present in Western European and Anglo-American historiography since the first half of the 20th century, starting with the American philosopher and historian Arthur Lovejoy (1940) and his Journal of the History of Ideas. The German tradition of the so-called history of the mind/spirit (Geistesgeschichte) was also influential. From the initial basis of the history of ideas, intellectual history has developed into a series of directions and approaches, taking often specific methodological paths and meaning different levels of interdisciplinarity: these are, for example, the history of concepts or Begriffsgeschichte in Germany, the history of political thought within the so-called Cambridge school, intellectual history as a link between socioeconomic and political phenomena with the history of literature at the University of Sussex, etc. This is precisely why intellectual history offers a desirable framework for researching the phenomenon of modernity, which almost necessarily means analyzing an urban (sub)context. Various problems of understanding, defining or developing attitudes towards modernity and its role in the dominant discourses of certain periods are questioned here at the level of texts on modern architecture (intellectual history) in relation to the city of Zagreb as a spatial research determinant (urban history). The main thesis is that the discourse on modern architecture, i.e. defining its origin, development and wider acceptance at a textual level sheds light on different political, socio-economic, cultural and intellectual aspects of the social development of Zagreb (and Croatia/Austria-Hungary/Yugoslavia in general). The topic connects several levels of intellectual history in parallel: as the history of ideas and concepts, the history of urban elites (occupations, certain types of intellectuals) or intellectual debates and controversies. The primary sources of this research are numerous texts by architects and other intellectuals interested in the emergence, affirmation and development of modern architecture in the long run of modern architecture. That is precisely why the years 1900 and 1980 are chronological determinants, representing clear intellectual breaking points: Viktor Kovačić publishes his manifesto "Modern Architecture" in 1900, and in 1980 a large round table discussion on the phenomenon of postmodernism in architecture is published in the magazine Arhitektura (Architecture). Starting from Kovačić and his manifesto, this thesis follows the long duration of an idea that is textually defined and communicated, both to the profession and to the general public, political elites, other intellectuals, etc. By analyzing key texts by experts on architecture and modern architecture a more complete picture of the history of an idea is provided. The thesis provides an answer to the question of what were the constituent elements of that idea at a certain moment in the past and why exactly those elements were highlighted. Between Kovačić's manifesto in 1900 and 1980, important texts appeared in the public domain that, each in their own way, influenced the discussion of modern architecture and its definition in a wider social context: from Kovačić to the collapse of the Habsburg Monarchy, K. Strajnić, A. G. Matoš, V. Lunaček, P. Senjanović and others join this discussion, from 1918 to the end of World War II main texts are written by D. Ibler, E. Weissmann, M. Krleža, S. Planić, B. Rajakovac, P. Knoll, Z. Požgaj, A. Albini, J. Seissel, V. Antolić, A. Freudenreich, K. Ostrogović, etc., and for the period from 1945 to 1980 (in addition to the already mentioned authors who continue to participate in the discussion) A. Mohorovičić, N. Šegvić, A. Mutnjaković, S. Sekulić-Gvozdanović, A. Pasinović, R. Ivančević, Z. Kolacio, T. Premerl, D. Venturini and many others are part of the discussion. The goal of this research is to systemize, analyze and contextualize key texts of architects (and other experts) who discussed the idea(s) of modern architecture. First of all, this implies reading and connecting the sources with the socio-historical context. Such an approach implies connecting the spheres of urban history with social history as well as political history. Zagreb stands out as an example, first of all because it is an undeniable Croatian center since the 19th century and is a logical choice due to the formation of the idea of modern architecture in Croatia in general, as well as the later center of (domestic) education of architects and their professional activity. Because of all this, the question of modern architecture often arises in the context of discussions on the city itself. In addition to the above, the intellectual history of architects and their texts also reveals the interrelationship of Croatian architecture with important external influences (Central Europe, Western Europe, Eastern Europe, the Soviet Union and the United States), that is, it looks at the extent to which Croatian architects are international, and to what extent their texts correspond to the situation in Croatia, i.e. Zagreb. Modern architectural tendencies started emerging in Croatia at the turn of the 20th century. At the same time, a vivid intellectual discourse – on the notions of modernity, the principles of modernism, and its importance to the society – was blooming under the influence of Vienna and Otto Wagner's school of thought, especially Adolf Loos. At the beginning of the 20th century, architects were still educated at foreign universities, primarily in Vienna, but also in France and Germany. Immediately at the beginning of the interwar period, in 1919, the schooling of future architects will begin in Zagreb. Beside the important Technical College, which in 1926 would become part of the University of Zagreb as the Technical Faculty, especially the Architectural department of the Academy of Fine Arts under the leadership of Drago Ibler brought dynamics to education and different approaches to architecture in Croatia. The expansion of the city of Zagreb and the constant increase in the number of inhabitants, as well as the redefinition of the city's borders, represent a challenge not only to architects, but also to the city itself. The interwar period laid the foundations for the acceptance of modern architecture. The dissolution of Austria-Hungary in 1918 marked an important turning point which heavily influenced the intellectual discourse on modern architecture in Zagreb. The development of modern architecture and the changing political context – the formation of the Kingdom of Serbs, Croats and Slovenes; the later Kingdom of Yugoslavia; as well as the formation of the Independent State of Croatia in 1941 – were reflected in the discussions and nuances of the perceptions of modernity, a process which modified the role of the architect itself. During World War II the extraordinary dominance of politics directly reflected on the concept of modernity. Discussions on the principles of modern architecture continued after the end of World War II and the formation of the socialist Yugoslavia in 1945. However, the discourse was modified and adapted to the new political and social changes, which were caused by war. This led to important modifications in the presentation of the programme of modern architecture, as well the role of the architect and the architectural profession in urban environments (Zagreb in particular) and society in general. By the end of the war and the (re)establishment of Yugoslavia, modern architecture once again became the reference point of the new regime and directly connected to its modernization matrix. In doing so, modernist principles are reexamined, and in some cases ideologically harmonized. After the definitive rejection of influence from the Soviet Union, architecture took advantage of the opportunity in the coming post-war/Cold war reconstruction and construction, combining foreign influences with domestic needs. In this period, the connection between architecture and urban planning is most visible, which is especially reflected in Zagreb. This dominantly harmonious situation lasted until the end of the 1970s. The emergence of more individual approaches and stratification of principles marked the beginning of new aspirations in the form of postmodernism. By analyzing key texts on modern architecture, written primarily by architects (and also other well-informed intellectuals), essential sources for the intellectual development of the concept of modernity in Croatia and Zagreb are reevaluated and contextualized.