Winding through the verdant rainforest of Tenorio Volcano National Park of Costa Rica, is a bright blue river called Rio Celeste. The river is formed by the confluence of two smaller rivers called the Sour Creek and the Good View River. At precisely the point where the waters of the two completely transparent rivers meet, that the blue color starts. For that reason, this point is known as El Teñidor, which means “The Dyer” in English.

Until very recently, scientist were unable to fully explain why Río Celeste has such a distinctive turquoise coloration. Many hypotheses were put forward such as the water contained copper or calcium carbonate and sulfur, or that the river’s proximity to the Tenorio Volcano caused it have the blue color. It is now known that the blue color arises due to a physical phenomenon known as Mie scattering triggered by the presence of certain minerals in the river’s water that causes sunlight to reflect in such a manner that it gives the water its incredible hue.

Photo credit: The Rohit/Flickr