"Lake Shumarinai" is a dam lake created accompanying the construction of the Uryu Dam, and as an artificial lake, it boasts Japan's number one vastness, and its surface area is approximately 30 Tokyo Disneyland portions. In 1974 (Showa 49), the entire area of Lake Shumarinai, which was designated as a prefectural natural park, has pristine areas that receive strict regulations for nature conservation, and even now still retains nature's original form.

The lake, where large and small 13 islands float, shows the face of each season. The intricate terrain, reminiscent of Northern European fjords, nurtures the lake's creatures and deep primeval forest, and the lake surrounded by that deep nature is called a mysterious lake where "Ito," Japan's largest freshwater fish known as a phantom fish, inhabits. In the trout season, anglers visit from inside and outside the prefecture, and sometimes even from overseas, and in winter, it shows liveliness with smelt fishing.

In the summer camp season, many camping guests visit. Partly because it has hardly been commercialized as a tourist spot, its popularity is high among experienced campers and riders, and also the fact that there are many repeat visitors as "a place where one can calmly and leisurely spend one's own time" is one of its characteristics.