Female hiker resting beneath a waterfall along the vibrant blue Rio Celeste river in Tenorio Volcano National Park, Costa Rica.

- Image ID: BDE27M
Carver Mostardi / Alamy Stock Photo
Image ID: BDE27M
Surrounded by primary cloud forest and rainforest, The Rio Celeste in Tenorio National Park is one of Costa Rica's best kept secrets. The light blue color of the river and waterfall is the result of a volcanic chemical reaction, resulting in the mixture sulfur and calcium carbonates.
Location: Tenorio Volcano National Park, Alajuela, Costa Rica.