ENThe cultural heritage of modern architecture is a widely acknowledged phenomenon; however, unique urban landscapes that have witnessed a fundamental transformation in urban life in the 20th century are still underrepresented on the UNESCO World Heritage List. In this paper the built urban heritage of Kaunas city (1919–1939) is investigated as an example of a modern urban heritage site with a problematic focus on defining the attributes of urban heritage, especially when intangible heritage values are added to the tangible built heritage. In this paper the attributes of modern urban heritage are discussed on the example of “Modernist Kaunas (1919–1939): Architecture of Optimism”, the nomination dossier for the UNESCO World Heritage List. Three groups of attributes are described using historical research and later discussed by applying the method of comparative analysis. The conclusion proposes that Modernist Kaunas can fill the gap by representing Eastern European modern urbanity and enhance the understanding of the modern global city by reflecting the metropolitan aspirations in modern Europe. Keywords: modernist architecture; modernist urban heritage; Kaunas modernism; architecture of optimism; Lithuania; UNESCO world heritage. [From the publication]