There are more ways than one to perceive a city. In THE URBAN METABOLISM the urban landscape is considered as a complex, vast and interactive system that continuously works to meet the needs of its inhabitants. The publication is arranged like a matrix: Along the one axis run nine lines, each covering a single flow. These are air, water, biota, food, energy, waste, humans, cargo, and finally sand, sediment and construction materials. The International Architecture Biennale Rotterdam (IABR) asked the Netherlands Environmental Assessment Agency (PBL) to investigate on a global and national level what the separate key issues and bottlenecks for each flow actually are. Along the other axis, the work of the IABR Project Atelier Rotterdam shows all of the flows in context, presenting a first synthesis of the metabolic approach as well as proposals for pilot project on specific locations in Rotterdam. There are more ways than one to perceive a city. In THE URBAN METABOLISM the urban landscape is considered as a complex, vast and interactive system that continuously works to meet the needs of its inhabitants. The publication is arranged like a matrix: Along the one axis run nine lines, each covering a single flow. These are air, water, biota, food, energy, waste, humans, cargo, and finally sand, sediment and construction materials. The International Architecture Biennale Rotterdam (IABR) asked the Netherlands Environmental Assessment Agency (PBL) to investigate on a global and national level what the separate key issues and bottlenecks for each flow actually are. Along the other axis, the work of the IABR–Project Atelier Rotterdam shows all of the flows in context, presenting a first synthesis of the metabolic approach as well as proposals for pilot project on specific locations in Rotterdam.