The topic of the paper is an analysis of the origin and development of open areas in the examples of historical centers of Croatian coastal cities of Zadar, Šibenik and Trogir, through which their genesis, together with structural and morphological features, was ascertained. The paper also describes the historical development of urban matrices of the cities, on the basis of which the relationship of public open spaces and built space was observed. The research was conducted through a detailed review of historical literature, cartographic representations and photo documentation. Having evaluated the three selected cities, we were able to draw conclusions on the uniqueness of each of the examples due to different urban complexes in which public open spaces came into existence, as well as different spatial factors and historical circumstances that influenced the overall development of historic cores. Open public spaces have been important components of urban planning since ancient urbanism. Throughout history, streets and squares in front of sacral and communal buildings have been centers of public life of the people that inhabited walled cities. In the 19th century, when the danger from enemy armies came to an end, new types of public open spaces arised in a form of landscape city parks. Most often located in former military fortifications and within areas of former walls, the parks were created in the outskirts of cities, often forming a green belt around old city centers.