Around the world, cities are growing. Already, roughly 180,000 people move into cities every day. By 2015, the UN estimates that there will be 22 metropolitan areas with populations of more than 10 million people. Growing urban populations mean more costs for cities - from increasing energy use, to overstrained public services - but they also provide a stimulus for innovation. After all, we can’t infinitely expand outwards and upwards. Instead, we need to find ways to be more ‘efficiently urban’: in other words, we need to be smarter with how we use our resources, time and capital.