Rahul Mehrotra: The architectural wonder of impermanent cities

Every 12 years, a megacity springs up in India for the Kumbh Mela religious festival — what's built in ten weeks is completely disassembled in one. What can we learn from this fully functioning, temporary settlement? In a visionary talk, urban designer Rahul Mehrotra explores the benefits of building impermanent cities that can travel, adapt or even disappear, leaving the lightest possible footprint on the planet.