This article is part of our Urban Expeditions series, an initiative made possible by a grant from United Technologies to the National Geographic Society. As the world’s urban population expands, architects and planners are mapping out ways to make cities more sustainable. Cities produce a vast amount of emissions and waste, putting a strain on both human and ecological health. But our buildings themselves may hold a solution. High-density urban areas—especially those built using green methods in design and construction—can be more energy efficient and pollute less. New research is also revealing that green buildings can actually be good for our health too. The infographics presented in this article is useful.