The Netherlands has a tradition in public spatial planning and design. In the past 20 years, we have seen an increasing role for the market in this field, and more recently, growing attention for sustainability. Sustainability has become an economic factor. Not only at the building level, but also on the level of large-scale area development projects. More and more local governments have high ambitions for sustainable development. Increasingly, during project development, buildings are developed on a sustainable basis. Most of the time, the focus in this approach is on energy. However, sustainability also comprises social aspects. Energy measures have a direct relation to an economic factor such as investment costs, and payback time can be calculated. The economic aspects of social sustainability are more complex. Therefore, for all sustainability development projects, especially in large-scale projects planned over a longer period, it is necessary to make presumptions, which are less reliable as the planning period is extended. For future larger-scale developments, experience in the Netherlands points to two design approaches: ‘backcasting’, or using a growth model (or a combination of these two). The power of design is the ability to imagine possible scenarios for the future. The layer approach helps to integrate sustainability into public spatial planning. And more specifically, Urban Design Management (UDM) supports an integrative and collaborative approach also on the operational level of a project in which public and market partners work together. This article outlines how design, based on these approaches, can contribute to sustainable development based on the ‘new playing field’, where spatial problems should be solved in networks. Dutch projects in Almere (Benoordenhout) and Rijswijk are used to illustrate this approach.