With 1.62 million inhabitants, Barcelona is one of the most densely populated cities in Europe. Located between the Mediterranean Sea and the mountain range of Collserola, the city has urbanised virtually all available land after various periods of urban expansion. This has led to conflicting pressures over green space. This film presents some of the ways in which Barcelona has tackled problems resulting from urban expansion such air pollution and rising temperatures, and shows how a strong ambition to protect urban green space and its functions have contributed to human health, well-being and the quality of life for urban citizens.