In 2014, for the first time, more people live in cities than in rural areas. By 2050, more than 70% of people are predicted to be living in cities. Such rapid growth and urbanisation creates tremendous opportunities and also tremendous challenges, both for the people who live there and for the environment. Can we rethink how we design and live in cities in the future? How will resources flow to and around them and how will cities adapt to the challenges they face?