Urban areas are currently facing significant new and/or aggravated existing challenges due to the impacts of climate change, including increased frequency and intensity of extreme weather events, urban greenness loss, urban flash floods, air quality degradation, and increased greenhouse gas emissions, geo-hazards, and urban heat fluxes among others. To address these challenges HARMONIA will provide a resilience assessment platform to help urban stakeholders understand and quantify Climate Change (CC) effects. In order to develop and apply the diverse methodologies and applications, four European cities are participating, Milan, Piraeus, Sofia, and Ixelles. Based on satellite and multidimensional urban context data, the HARMONIA platform will offer a user-friendly knowledge base, dispensing detailed information on a local neighborhood and building block level. This will support local decision-making and foster a wide range of applications dedicated to climate change adaptation and mitigation. Specifically, HARMONIA will focus on two types of Climate Change (CC) effects: Natural and human-made hazards intensified by CC, including urban flooding, soil degradation, geohazards (landslides, earthquake, ground deformation), heat islands, urban heat fluxes, air quality, and gas emissions.