Most people consider parks important for their quality of life, yet systematic causal evidence is missing. We exploit exogenous variations in their use values to estimate causal effects. Using a representative household panel with precise geographical coordinates of households linked to satellite images of green spaces with a nationwide coverage, we employ a spatial difference-in-differences design, comparing within-individual changes between residents living close to a green space and those living further away. We exploit Covid-19 as exogenous shock. We find that green spaces raised overall life satisfaction while reducing symptoms of anxiety (feelings of nervousness and worry) and depression. There is also suggestive evidence for reduced loneliness. Given the number of people in their surroundings, a compensating-surplus calculation suggests that parks added substantial benefits during the period studied.