The initiatory and poetic journey to which this book invites us is that of several paths, from Lyon to Marseille, which find their place and their history within the grand tapestry of the "Silk Roads" of yesterday, today, and tomorrow. The reader will retain two images: the first is that of a plot of vines, persistent and resilient, amidst the vast Rhône industrial site south of Lyon. The second is that of the Portes du Tarn, with its project committing it to developing and implementing, "here and now," innovative solutions that respect ecology—a scientific imperative for safeguarding the habitability of the world in the diversity of its territories. This book unveils the "circular economy" and its imperative regarding a public responsibility that takes into account social needs, their interfaces with the environment and nature, and, at the intersection of their material and energy flows, their representation within the financial system. Publisher: Presses de l'école nationale des Ponts et Chaussées. ISBN13 978-2-85978-528-4 224 pages Publication date: 03/01/2020