Designer Stefano Boeri is branching out from his skyscraper ‘forests’, to building an entire forest city in Liuzhou, China – that will fight the increasing issue of air pollution naturally. The 40,000 trees will absorb almost 10,000 tons of CO2 and other pollutants a year whilst producing a huge amount of oxygen, making it a much cleaner environment for the 30,000 people it will host. When can we move in?