Japan is a country of steep mountains surrounding wide flat plains where people have lived for thousands of years. On the largest plain lies the country's largest freshwater lake, Lake Biwa, which is not at all far from Japan's ancient, capital city of Kyoto. The slopes that stretch down towards the lake have been terraced. Here rice seedlings need shallow water in which to grow, and the neat, meticulously constructed paddy fields provide just this. Some of them have been cultivated continuously for thousands of years. Alongside them stand patches of woodland where, for centuries, the people have found their fuel and their food. This is a land that has been touched by people, yet the people tread lightly upon it. It's a land that has been ruled for centuries by the demands of the rice, yet it's still dominated by the rhythmic cycle of the seasons. Here is a landscape that the Japanese people hold so close to their hearts that they have a special word for it: satoyama.

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.