The idea that the city, with its overall structure, spaces, infrastructures, and environment, could play an essential role in its inhabitants’ psychological wellbeing and physical health is a relatively recent emerging concept directly connected to the growing awareness on urban health issues. In particular, the green open space of the city has changed perception in this sense due to medical developments on the one hand and social changes on the other. Public open spaces, squares, gardens, and boulevards were mainly created as an element of urban decoration and for certain socialisation functions, but since the nineteenth century, they have started to be thought of as tools to ensure hygiene standards in the modern city. Urban green and health have long gone their separate ways, whereas, since the rise of industrialisation, have increasingly been conceived as interconnected, playing a crucial role in urban policies for the improvement of citizen's wellbeing. Through the critical analysis of medical and urban literature connected to urban green spaces and health, this contribution investigates the rise and growing potential of urban green spaces as crucial elements to improve the psychological and physical wellbeing of citizens, giving compelling proof of the urgent need of an effective contemporary strategy for sustainable and resilient cities and communities.