Walking in a park, swimming in a lake, cultivating flowers... What if these activities, practiced in a group and shared with others, were offered to fight loneliness and to improve wellbeing in cities? RECETAS (Re-imagining Environments for Connection and Engagement: Testing Actions for Social Prescribing in Natural Spaces) is a project funded by the European Commission's H2020 program. Our goal: develop and test green and social activities to improve the physical and mental health and well-being of urban citizens. Our consortium, composed of 13 institutions from 9 countries, is using multidisciplinary approaches to imagine and implement 'Nature-based Social Prescribing' in 6 pilot cities worldwide.