The concept of a nature-based solution (NBS) has been developed in order to operationalize an ecosystem services approach within spatial planning policies and practices, to fully integrate the ecological dimension, and, at the same time, to address current societal challenges in cities. It exceeds the bounds of traditional approaches that aim 'to protect and preserve' by considering enhancing, restoring, co-creating, and co-designing urban green networks with nature that are characterized by

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... tifunctionality and connectivity. NBSs include the main ideas of green and blue infrastructure, ecosystem services, and biomimicry concepts, and they are considered to be urban design and planning tools for ecologically sensitive urban development. Nowadays, NBSs are on their way to the mainstream as part of both national and international policies. The successful implementation of NBSs in Europe and worldwide, which is becoming increasingly common, highlights the importance and relevance of NBS for sustainable and livable cities. This paper discusses the roles, development processes, and functions of NBSs in cities by taking Leipzig as a case study. Using data from interviews conducted from 2017 to 2019, we study the past and current challenges that the city faces, including the whole process of NBS implementation and successful realization. We discuss the main drivers, governance actors, and design options of NBSs. We highlight the ecosystem services provided by each NBS. We discuss these drivers and governance strategies by applying the framework for assessing the co-benefits of NBSs in urban areas in order to assess the opportunities and challenges that NBSs may have. This way, we are able to identify steps and procedures that help to increase the evidence base for the effectiveness of NBS by providing examples of best practice that demonstrate the multiple co-benefits provided by NBSs.