Tenorio Volcano National Park in Costa Rica is home to a river plagiarized from a fairy tale. The Rio Celeste is a turquoise wonder, turned neon by nature. It's all about the minerals, Marie: the river's blue hue results from a mixture of sulfur and calcium carbonate that comes from the nearby volcano.
It's a bit of a shlep to get to the Rio Celeste—you need to hike for an hour through the park. The further upstream you go, the brighter the blue becomes. You'll see a gorgeous waterfall and may spot a tapir or two along the trail. The ultimate destination is Los Teñideros: the spot where two clear rivers converge and the blue Rio Celeste appears as if by magic.
A river runs through it:
View Tenorio Volcano National Park - Rio Celeste in a larger map