Freiburg, Germany, near the southwest end of the Black Forest, is one of the most sustainable cities in Europe, and for good reason. Pedestrian-friendly streets; solar-powered neighborhoods; turning waste into biomass energy—Freiburg has become a real-life example of how a city can thrive sustainably. For travelers who care about nature and want to see how urban life and sustainability can coexist, Freiburg, Germany is a living, breathing model of change. This is, in fact, why many people c...