The area around the Maashaven in Rotterdam South is short of larger recreational public space, which is a drawback to attract starters and young families to this socially segregated area. Like in many other Northern European cities, the harbour currently divides successful and the deprived neighbourhoods and awaits a new function now the previous industry and trade dominated relation between city and river disappears. Therefore in this thesis it is investigated how inner city former harbour bays can function as public space in order to stitch disassociated districts into a continuum and to strengthen the relation between city and river. This question comprises hypotheses: that water can function as public space and that creating public space is a valid strategy to reconnect disassociated districts. Four sub-research questions are formulated. Firstly it is investigated how the relation between city and river has developed and how a design could influence this relation. Secondly, criteria for good public space in harbour areas are studied. Since the former harbour function slowly disappears, the contemporary and future spatial claims for this area are investigated at the third sub-question. As fourth question, the main varaible spatial preconditions are investigated to be able to make a design that can adapt to different future scenarios. This thesis uses research by design on the case of the Maashaven as main method to which design research such as literature study, plan analysis, comparative study and a scenario study are supportive. After formulating a vision on the area, an adaptive redevelopment plan is designed. Two robust interventions that could function as initiators of change in the area are further elaborated. They illustrate the meaning of the design on different scales and together cover all aspects of the scenario study and most stakeholders perspectives. The combination of design research and research by design leads to some generic and some site specific conclusions. Firstly, transforming a harbour basin into public space depends largely on the design of a selection of spaces at its edges. Nor the whole basin, nor all quays should be made public. Secondly, the strategy to reconnect districts cannot only consist out of public space design but also requires a good slow traffic network, a strong identity and an appealing mix of program. In the case of the Maashaven the spatial claims of industry and inland shipping, recreation and ecology showed to be compatible and can even strengthen each other. Using inner city basins for floating neighbourhoods as the municipality proposes, is rejected mainly because of its privatising effect. On the contrary, a modest amount of floating constructions for recreational, nonpermanent use can strengthen the public character of the harbour. Thirdly, the relation between city and river can be strengthened by making the river and inner harbours part of the daily life of people again. For Rotterdam specifically the design showed how the relation between city and river can be strengthened on neighbourhood, city and regional scale.