Nature-based solutions are a comparatively new field of research regarding the 'green city' and a main focus of large European and Global research programs. Nature-based Solutions (NBS) are defined by IUCN as "actions to protect, sustainably manage, and restore natural or modified-in our case urban-ecosystems that address societal challenges effectively and adaptively, simultaneously providing human well-being and biodiversity benefits". NBS have the aim to support the achievement of society's development goals and human well-being and public health as well as social welfare in ways that reflect the cultural and societal values of the urban societies and enhance the resilience of ecosystems, their capacity for renewal, their diversity, along with the provision of services. NBS are designed to address major societal challenges related to cities, such as safe and clean housing, fresh air, food security, climate change, water supply, human health, and disaster risk. NBS are intended to produce societal benefits in a fair and equitable way, thus promoting transparency and broad participation as well as learning and education. This Special Issue provides a state of the art of the functional, empirical, and field study-based experiences and data on NBS provided by green and blue infrastructure (GBI) in cities. We focus on the interaction of the instrument of NBS, its benefits, and tradeoffs with urban land, the built environment in cities, and the urban society, in particular in relation to social wealth and public health, also taking into account stewardship and governance aspects.