Cities are complex and dynamic systems in continuous evolution, whose metabolism is source of massive pressures on the environment and human health. Therefore, assessing the sustainability of urban metabolism (UM) is essential to disclosure environmental impacts, reduce their negative effects, and eventually support a sustainable design and management of urban spaces.On one hand, a plethora of models, methodologies, and tools were proposed to identify main patterns of consumption and profiling best practices to minimize the related impacts. These are mostly based on detailed linear compilations of life cycle information on UM inputs and outputs. On the other hand, promising efforts were made in revealing the non-linear relationships and cause-effect chains among the UM elements. In this case, the analysis may go well beyond a static input>black-box>output modelling framework. The two modelling perspectives show both pros and cons, and their combination seems an effective solution to exploit their complementary functions.ESTIMUM aims to develop an integrated spatially-explicit dynamic modelling and operational tool for scenario analysis of UM designed to assess the value of ecosystem services under different socio-economic and environmental conditions. Such a tool is built using a system dynamics rationale, and is suited to characterise the complex relationships between biosphere and technosphere components in urban regions. While the former are components of urban ecosystems (stocks and flows of biotic and abiotic elements, semi-natural systems, etc.), the latter are stocks and flows of infrastructure and commodities (goods and services of the UM), mainly associated with life cycle product and input-output economic sectorial datasets. Such an integrated structure represents the intra- and inter-linkages among the components of a city (both man-made and natural ones), disclosing metabolic pathways and allowing to trace inputs and outputs of a urban system in relation with the surrounding environment, at multiple scales (city > region > country > Earth).Hence, the main output of ESTIMUM is a toolbox for the valuation of ecosystem service trade-offs (e.g. air purification, noise reduction, urban cooling, runoff mitigation, food provision) in urban regions, which can support the urban planning by simulating physical and socioeconomic benefits and costs of solutions to enhance the supply of ecosystem services in cities. Three municipalities are put forward to test the robustness of the tool and its relevance for Luxembourg, which is considered a showcase for Europe. Esch-sur-Alzette (located in the South of Luxembourg) is taken as a demonstrator and compared with Lisbon (Portugal) and Siena (Italy). Because the proposed simulation framework evaluates changes in urban ecosystem service trends over time and different uses of land, a special focus is on improving the urban biodiversity and management of green spaces, while at the same time fostering the implementation of nature-based solutions in the cities. Accordingly, ESTIMUM offers an unprecedented monitoring, simulation and management tool to support sustainable urban planning policies through prospective assessments and trade-offs analyses. The toolbox is going to be validated in test-bed conditions by policy makers in Luxembourg and outside, and fed with inputs from a number of key-players and experts in UM, ecosystem services and sustainable urban planning.In this regard, ESTIMUM contributes to meeting national research and policy targets oriented towards a conceptual construction, organisation and practical use of the urban space, fostering the long-term socio-economic and environmental development in Luxembourg through nature-based solutions’ implementation, and improving the future quality of life within the country.