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In cities, rivers can contribute significantly to quality of life. The transformation of riverfront areas in Germany from transit zones of the carfriendly city to spaces of movement and encounter for pedestrians and cyclists is a complex and protracted process. In many cities, main traffic arteries interfere with integrated urban development, creating barriers for nonmotorized, physically active mobility. Frequently, the rivers themselves are federal waterways, meaning that responsibility for them lies not with a municipality, but with a federal agency, which complicates planned modifications of riverfront zones. Involved as well are growing demands for flood protection and climate adaptation. Finally, transformations in commerce and remote working represent a fundamental shift in the utilization of downtown areas, and this includes open spaces and public ground-floor zones along downtown riverfront areas. Why, then, address the promotion of health and mobility as an additional aspect when designing downtown riverfront zones?

In cities, large, interconnected surfaces of water, our so-called blue infrastructure, contribute substantially to the promotion of health and to climate adaptation. A »blue space« is defined as an outdoor space whose identity is shaped by bodies of water, because it is either physically accessible or perceptible in audiovisual terms. Examples include coastlines, riverbanks, lakes and canals, and squares with pools or fountains. These offer numerous possibilities for coming into contact with water on a daily basis: people may enjoy the sight, sound, smell, or feel of being near water; they may be active on or near water, by cycling, jogging, swimming, rowing, sailing, or traveling via water taxi. Blue spaces therefore feature a multitude of health-promoting amenities that enhance the quality of life; they can even be quantified in relation to the increased life expectancies of local residents (Roe et al. 2021).

The term walkability refers to the potential of a built environment to promote active bodily everyday mobility in the general population (Bucksch et al. 2014). In general, we distinguish between five different dimensions: there is the density and diversity of utilizations, the accessibility of destinations, the distance to the public transport infrastructure, and the design of urban space (Ewing and Cervero 2010). From the perspective of urban planning in Germany, walkability is being discussed to an increasing degree against the background of climate protection, as well as of the enhancement of the urban fabric (Tran 2018). At this point, however, there are very few up-to-date studies on the reconfiguration of downtown riverfront zones in major German cities. The aim of this essay is to elaborate relevant structural aspects as well as planning strategies designed to optimize the positive public health impacts of blue spaces. Investigated for this purpose, with reference to the case study of the Mainkai in Frankfurt, Germany, are the value and the role of walkability in municipal planning instruments, as well as structural and programmatic developments over the past thirty years.