The city of the future needs to be a green city. Several scientific studies associate green spaces -urban parks, gardens, tree-lined streets or forests, among others- with numerous health benefits in adults, such as a reduction of stress, a longer life or a better general and mental health. Studies in children have shown positive associations between green environments and better attention capacities, emotional and behavioural development, and even beneficial structural changes in the brain. The impact of blue spaces – fountains, lakes, rivers or oceans – on our health is a relatively new field of research. Blue spaces are associated with higher levels of physical activity and could be beneficial to our mental health, particularly in terms of stress reduction and self-perceived well-being.