Lake Shumarinai is a dam lake created with the construction of the Uryu Dam. It boasts the largest area of any man-made lake in Japan, with a surface area equivalent to about 30 Tokyo Disneylands. The Lake Shumarinai area, designated as a prefectural natural park in 1974, is a vast wilderness area subject to strict nature conservation regulations, and it still retains its original natural form.

The lake, with its 13 large and small islands, shows different faces in each of the four seasons. Its intricate topography, reminiscent of a Nordic fjord, nurtures the lake's creatures and deep primeval forests. Surrounded by this profound nature, it is called a mystical lake, home to the 'Itou' (Japanese Huchen), Japan's largest freshwater fish, known as the phantom fish. During the trout season, anglers visit from both within and outside of Hokkaido, and sometimes from overseas. In winter, it bustles with smelt fishing.

During the summer camping season, many campers visit. As it is largely undeveloped as a tourist destination, it is popular among experienced campers and motorcycle riders. One of its characteristics is the high number of repeat visitors who see it as 'a place to relax and spend one's time quietly'.