Bishamon-numa Pond is the largest of Goshiki-numa lakes (the five-colored lakes). It is located at 770 m above sea level, has an area of 100,000 m2, and is 13 m deep at the deepest point. The degree of clearness is 4-5 m, which is not very high. The pond looks beautiful white blue on a fine day. The color of the pond changes, ranging from red, blue, green, and cobalt blue to emerald green with the season, the weather, and the position of the sun. The most beautiful is when it looks emerald green, which will dazzle your eyes. The water is strongly acidic. When the sunlight reaches fine particles of aluminum silicate that are deposited at the bottom of the pond, the light is scattered and the color of the pond changes. Also aquatic plants growing in the pond take on greenish color when the water temperature rises. If the sunlight pours onto those plants and the fine particles, the pond looks red or blue. When the water surface is as calm as a mirror, Mt. Bandai and surrounding green or red leaves are reflected on the water, which is very impressive. It is said that the water flows from Ruri-numa Pond, but there is a spring somewhere in this pond itself. The water of this pond flows down into Lake Inawashiro.