The current urban discourse is imbued with the smart city concept. The smart city is based on innovative urban planning based on smart technologies that cities are not only safer and cleaner, but especially efficient. But cities are actually better? In the book about Smart Cities. visualizing the challenges for 21st century urbanism keep Maarten Hajer and Ton Dassen (PBL - PBL) is a plea for a 'smart planning', and thus provide a counterweight to the uncritical embrace of the smart city. Smart planning needs solutions find that in the twentieth century urbanism is forgotten: the metabolism of cities - the wide variety of input and output streams that connect the urban life with nature. 50 infographics this metabolism visualized. book about Smart Cities. visualizing the challenges for 21st century urbanism will be presented at the International Architecture Biennale (IABR) 2014 Urban by Nature.