This book is a contribution to the social debate about the city and its future. It proposes the idea of the city of proximity, or the "15-minute city" a city where everything you need on a daily basis is just a few minutes away. But not only. In short, a city built from the life of its citizens and from an idea of habitable proximity in which they can find what they need to live, and to do it together with others. The basic theme of this book is therefore this: can we build the contemporary city starting from a new idea of proximity? The answer it proposes is yes we can. Many cities in the world, including Paris, Barcelona and Milan, have made commitments and are taking steps in this same direction, proposing concrete anticipations of what this city of proximity can be.