A strange structure is taking shape in the rolling green hills of southern England: Engineers are building "Eden" - an enclosed garden the size of thirty football pitches. A sixty metre deep crater is being capped with space-age plastic domes that will be home to thousands of rare plants. The lightweight galvanized steel tubular frames are going up to form enormous self-supporting shells. A computerized production line calculates the length of each of the shell sections and automatically cuts them to exactly the right size. Eden will act as giant laboratory where scientists can study the complex relationships that make this planet work. The Japanese have recreated the ocean with the world's largest dome covered beach. Measuring an incredible three hundred metres in length, this man made ecosystem was designed to reproduce everything from rolling surf to a jungle with live giraffes. The dream of creating a self-sustaining ecosystem has been studied for thirty years by NASA. We'll check in with NASA engineers for the latest glimpse of sustainability on distant planets and space stations.