The INTErventions, Research, and Action in Cities Team (INTERACT) is a pan-Canadian collaboration of scientists, urban planners, and citizens uncovering the impact of urban changes on health and equity. The city is our living laboratory. We document its transformation through geographic information systems, while precisely measuring physical activity, social participation and the well-being of populations using innovative technologies such as GPS, accelerometers or mobile applications. With big data and various methods of analysis such as artificial intelligence, we identify how these urban transformations influence health profiles and social inequalities. Our work helps decision-makers and citizens orient future investments for livable, sustainable, and equitable urban development.