Cities are the sustainable hub of the future, where over 80 percent of our population will eventually live. If we can't make cities sustainable, we can't make the world sustainable.
(Terry Goss/Wikimedia Commons https://commons.wikimedia.org/wiki/File:White_shark.jpg)
When people walk down the street, rarely do they ponder the subsurface infrastructure beneath their feet — including hidden waterways. (Yeshi Kangrang/Unsplash)