What if cities learned to absorb rainfall, neutralise floods and turn their streets green in the process? Meet Kongjian Yu, a Chinese architect doing just that. ‘We can make friends with floods,’ he says of his work to limit dangerous water levels in 250 cities across China. ‘Sponge cities allow the natural flow to come back. We use a wetland system, a spongy system to retain the water instead of draining it away.’ As sea levels creep up and extreme rainfall becomes more common around the world, could this be a way to protect our cities?