Rio Celeste (Blue River) waterfall in Tenorio Volcano National Park, Costa Rica. The blue coloration is a result of sulphur from the volcano seeping

- Image ID: HM7124
adrian hepworth / Alamy Stock Photo
Image ID: HM7124
Rio Celeste (Blue River) waterfall in Tenorio Volcano National Park, Costa Rica. The blue coloration is a result of sulphur from the volcano seeping up through the river bed and mixing with calcium carbonate in the water.