The beauty of the Rio Celeste waterfalls, nestled away in a Costa Rican rainforest, is more than just skin-deep. The unique coloration of the water is due to a fascinating geological phenomenon, where the mingling of minerals in the river creates a chemical reaction that causes the water to turn an intense shade of blue, or celeste. But you can’t miss the star of the tour! The Rio Celeste sloth sanctuary is home to some of the cutest and most fascinating creatures on the planet.