The Blue Pond is located on the left bank of River Bieigawa near the town of Biei in Hokkaido Island, Japan.
Interestingly, it is not a natural formation. The artificial pond was created when a dam was built to protect the area from mud flows due to its proximity to a volcano on Mt. Tokachi. When the volcano erupted in December 1988, local officials decided to construct the dam upstream along the river. All the water blocked by this dam gets collected in a depression in the forest, creating the pond.
It’s not just the striking blue that sets the pond apart, but also the barren tree stumps that protrude from the surface of the water. Also, the color of the pond hardly remains constant. It keeps varying based on the season, and the viewing angle. In a certain light and angle, the electric blue pond appears to be a lovely green instead. This unusual phenomenon has no real scientific explanation. Some theories attribute it to a high concentration of aluminum hydroxide in the water. The naturally occurring mineral is known to reflect the shorter wavelength blue light, just like the earth’s atmosphere does. Of course, the water itself is colorless.