Eckart Wurzner is a mayor on a mission to make his city climate neutral by 2030. Under his leadership, the city of Heidelberg is buying a fleet of hydrogen-powered buses, building a network of bicycle superhighways to the suburbs, and designing neighborhoods to discourage all vehicles and encourage walking. The city had an opportunity, starting in 2009, to redevelop an area called the Bahnstadt. Modern apartment buildings in the development are so well insulated, they require almost no energy to heat. Cars are not banned in the Bahnstadt, but there is almost no traffic. Virtually everything that residents need, including jobs, is available in the community. “The idea is to get back to the classic early city, where living and working are closely intertwined,” said Ralf Bermich, head of the city’s Office of Environmental Protection.