Background: Some components of healthy aging including physical activity, social participation or mobility have been linked to dimensions of the built environment, but a more profound understanding of the processes linking environments to health among older adults is still lacking. Given the challenges of aging populations and growing urbanization in industrialized nations, calls have been issued for more sustainable urban (re-)development and implementation of local solutions to address global environmental and health problems. However, to date, few studies have considered older adults' daily mobility in order to better understand how both individual social, cultural or financial resources and the presence of local environmental resources or hazards, transportation infrastructures and urban form, either contribute or are detrimental to healthy aging. Novel ubiquitous wearable sensors offer a means of gathering continuous information on people's location, levels of physical activity, perceptions or feelings. Combining such sensor data with classical questionnaires on perceived environments and qualitative assessment of experience of places opens new opportunities to assess the complex interplay between individual and environmental structure of opportunities. Objective: In response to current gaps and novel analytical capabilities, this project will develop an international platform and research agenda to collect and analyse detailed data on daily mobility and health outcomes among older adults participating in two existing cohorts and one developing cohort in contrasted urban settings in Montreal, Paris and Luxembourg. Methods: Our study will combine a multisensor device for collection of location (GPS) and physical activity (accelerometer), with questionnaires on perceived environments and well being and qualitative assessment of experience of places. We will thereby collect detailed data and conduct advanced quantitative and qualitative analyses to disentangle the complex people-environment interactions that link urban local contexts to healthy aging. Expected results: This project will (i) generate evidence about how characteristics of urban environments relate to active mobility, social participation, and well being, all of which are crucial dimensions of healthy aging, and (ii) contribute to the development of an international research platform on built environment and healthy aging.