Celeste River is a river in Tenorio Volcano National Park of Costa Rica It is notable for its distinctive turquoise coloration. The Celeste River also borders several hot springs and has one large waterfall.

It takes about an hour to hike to the waterfall from the park’s entrance. The source of the river’s distinctive turquoise color is not due to a chemical species but to a physical phenomenon known as Mie scattering.

Celeste River is fed by two colorless rivers, the Buenavista River and Sour Creek. Buenavista River carries a large concentration of aluminosilicate particles with a small diameter. Sour Creek, as its name implies, has a high acidity due to volcanic activity.

When these two streams mix to form Celeste River, the drop in pH causes the aluminosilicate particles to aggregate and enlarge to a diameter of about 566 nm. These suspended particles produce Mie scattering which gives the river a strong turquoise color.

Though the scientific explanation is great, my favorite theory is the ones believed by the ancient locals, that says that: when God finished painting the sky, He washed his brushes in these waters.

Whether following science, myth or just beauty, Rio Celeste is definitely a must-see-place when visiting Costa Rica.