Imagine a realm where the seasons' rhythms rule - where centuries of agriculture and fishing have re-shaped the land, yet where people and nature remain in harmony. Sangoro Tanaka lives in just such a paradise. At 83, he's a guardian of one of Japan's secret water gardens. Here - over a thousand years - towns and villages have developed a unique system to make springs and water part of their homes. From inside these homes, the streams pour into Japan's largest freshwater lake, Lake Biwa - an area 5 times the size of Paris - near the ancient capital of Kyoto. This is a habitat so precious the Japanese have a special word for it: "Satoyama" - villages where mountains give way to plains. They are exceptional environments essential to both the people who maintain them and to the wildlife that now share them.