9. Caño Cristales in Colombia
The Caño Cristales is referred to as the most beautiful river in the world due to the vibrant colors that appear within it. The majority of the river is red, which is caused by riverweeds at the bottom, while yellow, blue and black appear scattered among green moss on rocks in the river. These colors only appear during a short time period between the area’s wet and dry seasons from September through November when the water level is just right for the plant species to turn to their rich colors.