The main objective of the Action is to develop better representations of the urban systems interactions and dynamics as well as new configurations of urban areas so that they consume fewer resources, emit less pollution, are more resilient to the impacts of climate change and are more sustainable in general. It is widely recognised that urban areas need to curb greenhouse gas emissions, reduce consumption of resources and adapt to be more resilient to climate change impacts – and become more sustainable in general. Whilst many initiatives address aspects of sustainability, this Action is distinct in its focus upon assessment technologies for simulation and integrated assessment of urban areas from a multi-functional point of view at a whole city scale. Models, techniques and tools that are required to enable management of the highly connected technological, human and natural systems that make up cities are now emerging. Meanwhile, planning decisions are being made without sufficient understanding of long term changes, impacts and uncertainties. The implications for sustainability within Europe and internationally are critical. This COST Action will build a new European coalition of researchers equipped to address the intricate challenge of integrated assessment in cities. Whilst cultivating a diversity of multi-disciplinary approaches this coalition will develop collective understanding, share techniques and work jointly in disseminating results. This Action is a timely opportunity and suitable mechanism to take European research on urban integrated assessment from its current infant and rather fragmented state to being a consolidated and internationally leading activity.