Over-tourism has become a new subject for research, particularly on urban sustainable tourism, during recent years (Novy, 2018). The term refers to when the number of tourists at a certain time in an extreme way exceeds the number of locals in the destination (Goodwin, 2017). This phenomenon creates a series of problems for the host destinations and puts pressure on them and their attractions, on the local service facilities and the genuine urban culture (Postma and Schmuecker, 2017; Trancoso Gonzalez, 2018; Weber et al, 2017; Montanari & Staniscias, 2010). Earlier research has shown how this phenomenon results in tension/conflict between locals and tourists and creates phobia among host people towards tourists(Postma and Schmuecker,2017; Martins, 2018; Milano et al, 2018). Recent research (Koens et al, 2018) shows that tourism stakeholders in many European cities show great awareness on the issue in their cities. Earlier research has mostly focused on locals while a focus on the visitors has beenlacking.  The purpose of the research is to get more empirical insights in over-tourism in four European city centers, Dubrovnik, Visby, Stockholm, and Riga, from both perspectives of locals and visitors/tourists, and thereby get knowledge through the challenges to, and opportunities for, both constituencies that are created in this learning process. This is in consistence with earlier research with same purpose (Costa et al, 2018). The research is justified by the fact that the topic is still new, and there are not too many studies published as of now. The first common characteristic between these four cities is that they all are cruising ports. The two first cities are rather towns than cities, almost of same size and natural preconditions, while the latters are much larger, capital cities in the Baltic Sea region with almost similar preconditions i.e. Over-tourism in the downtown area during peakseason.  The overall methodological approach in this project will be qualitative consisting of triangulation (mixed methods) based on comparative case studies. The data collection methods will consist of: field observations during the peak season in July-August in the four cities, face to face interviews and email interviews