In recent years, cities have realized the representative and spatial contextualizing importance of water: Water creates spaces with great conditions to decelerate and stroll. It enlivens and structures urban spaces, without creating spatial borders. It enhances the value of urban spaces and can define a certain image in people's mind maps. A particular focus is set by the revitalization of urban waterfronts or former ports and qualitative enhancement of their spatial condition values: especially, if massive urban conversions take place and new (housing) districts transform the urban heritage. Hereby, the development of the areas at the waterfront has major importance enabling an appropriate insertion of human activities and agglomerations in an increasingly threatened and deteriorating environment. At the same time, the sustainable development of the waterfront can improve the chances of the respective cities and regions in the international competition. First, this paper is dedicated to the relationship of waterfront, city and sustainability. Then criteria are developed, which are crucial for a sustainable urban development at the waterfront. These criteria are clarified by examples of planning practice.

The urban waterfront has recently been the site of many municipal development projects all over the world. The popularity of this location has led to raging realestate prices, prestigious landmark architecture and masses of visitors and tourists. Besides the challenges that come with its popularity, the urban waterfront is also required to deal with current ecological challenges. This paper argues that there is another dimension that plays an important role in this scheme: The waterfronts nature as threshold. Considering its existence as a space between spaces may contribute to comprehend the phenomenon of the recent popularity of the urban waterfront and also its contribution to the city as a whole.

In times of the continuous transformation of urban structures in terms of growth and shrinkage, sprawl and the compact city, adaption and individuality, the only possibility for planners to cope with these circumstances while considering steadily changing parameters, is a strategic design approach. This means developing concepts based on variety, flexibility and stability at the same time: On the one hand, the intactness -or wholeness -referring to the existent context, on the other, the openness for future trends.Life cycles of cities and buildings are decreasing. Especially infrastructural systems which were generously created in the post-war period significantly shaping our landscapes are now shifted, transformed or revitalized. These spaces, together with the numerous industrial wastelands that are occurring, open up opportunities to become motors of city developments.It might be that the deficits in frequently criticized modern urban design practices are less related to the quality of individual buildings but rather in the neglect of gaps and the spaces in between them. As cities cannot be planned as a whole, but with subspaces being optimized partially independent from each other, the lack of coherence tends to create landscapes made of isolated fragments with an insular character, dominated by commercial districts, shopping malls, airports or museums.Strategic approaches for the post-industrial city pursue the re-appropriation of abandoned sites. With the means of innovative and unusual utilization concepts (temporary uses, promotion of public spaces, urban agriculture and others), formerly separated quarters can become part of a coherent spatial network -and therefore create a vibrant urban fabric appealing to its citizens.

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