Blue Pond in Biei, Hokkaido, Japan

Blue Pond in Biei, Hokkaido, Japan

Scientists aren’t exactly sure what causes the vibrant colour in Hokkaido’s Blue Pond. The water itself is not unusual, and appears clear. But at different angles, times of day, and depending on the light and distance, the water of this small pond near Daisetsuzan National Park can look electric blue or turquoise. The current theory centres on the relatively high concentration of aluminium hydroxide in the sediment at the bottom of the pond, which can reflect light in a bright blue colour.