a small copse of them. Up to 50 metres high, these steel-framed 'supertrees' not only have flowers and ferns growing up them but their metallic canopies act to absorb and disperse heat too. They’re equipped to harvest rainwater, too, as well as provide air ventilation for two “climate-controlled biomes” (large conservatories, in other words) below. Eleven of the 18 trees also boast solar panels along their ’branches’. 6 Water-producing billboard We live in a consumer world. And, so we don’t forget it, advertisers wallpaper our cities and highways with banks of billboards. Researchers at Lima’s University of Engineering and Technology have come up with a billboard with a difference. Using a system of condensers and filters, it traps the humidity in the air and extracts the water vapour to produce around 96 litres of drinking water a day. The public can help themselves to it for free. 7 Neo-walled gardens Gardens stopped being just the preserve of people’s front lawns long ago. For a while, roof gardens were all the rage. Now, it’s all about walls. Drawing on advances in hydroponics (growing plants without soil), the facades of a growing number of libraries and offices, shops and hotels are bursting into flower. One of the companies at the forefront of the “living wall” boom is UK-based firm Biotecture. The company’s “vertical gardens” can be seen