Guangzhou is one of China's most prosperous cities but its success is under threat by pollution and over development. Now, engineers are attempting to tide by the ultimate green building in the form of the Pearl River Tower; a skyscraper that is part power generator and all green. Uncover the story as engineers unveil a revolutionary method to tackle one of the hardest items to be recycled: Plastic. Meanwhile, planners attempting to tackle the chronic water shortage confronting the city hit one a state-of-the-art solution, nearly 20 metres underground.