Heidelberg is nearing completion of the Bahnstadt, one of the world’s largest carbon neutral districts. Built on a former brownfield site, this development includes passive-house construction, a combined heat and power station with district heating, green infrastructure to reduce the risk of flooding, access to transit, biking and walking paths, and more. We interview Wiebke Grosskopf, from the Heidelberg Office of Environmental Protection, to learn how the Bahnstadt works and what's next in its development.