The thesis of "Possibility of applying national park cities to tourism through a comparative analysis of London and Zagreb" is made with the assumption that greener, sustainable cities that support biodiversity and minimize negative effects on the environment are more attractive to tourists than cities with air, water and soil polluted. Given that current global challenges including pandemic, climate crisis, and biodiversity loss directly affect tourism activities, this paper seeks to identify how the concept of a national park city can serve to improve tourism supply and demand and increase attractiveness of a city as a tourist destination during climate crisis and coronavirus pandemic. This paper compares the biological and geological diversity and tourism of London and Zagreb. For this paper, primary research was conducted using the method of an in-depth, unstructured, and extensive interview with several experts in the field of tourism, environmental protection, and natural sciences. The results showed that Zagreb has the potential to be an urban national park, but lacks knowledge and understanding of the population about the importance of preserving and protecting urban biodiversity, which is crucial for the implementation of the concept of the urban national park. In the final part of the paper, the author presented her proposals, based on theory, analysis, and research on pre-works and guidelines for the establishment of an urban national park in Zagreb.