The spring water at Beppu Benten Pond has a surprisingly transparent cobalt blue color. The secret to this blue color is the unique karst topography of the area, where high-transparency water containing calcium reflects only blue light when illuminated by sunlight. It's said that 186 liters per second and 11 tons per minute of water spring out, which is surprising both in terms of its color and the amount of water that springs out.
4.4