A unique biological wonder, Caño Cristales has been referred as the "river of five colors," "the river that ran away from paradise," and "the most beautiful river in the world."

For most of the year, Caño Cristales is indistinguishable from any other river: a bed of rocks covered in dull green mosses are visible below a cool, clear current.

However, for a brief period of time every year, the river blossoms in a vibrant explosion of colors. During the short span between the wet and dry seasons, when the water level is just right, a unique species of plant that lines the river floor called Macarenia clavigera turns a brilliant red. It is offset by splotches of yellow and green sand, blue water, and a thousand shades in between.

This only happens for a brief period between seasons. During Colombia's wet season, the water flows too fast and deep, obscuring the bottom of the river and denying the Macarenia clavigera the sun that it needs to turn red. During the dry season, there is not enough water to support the dazzling array of life in the river. But for a few weeks from September through November, the river transforms into a veritable living rainbow.

Caño Cristales is located in a remote, isolated area not easily accessible by road. Adventurous tourists can now fly into the nearby town of La Macarena. From there it is a short trip to "Serrania de la Macarena," the national park in which Caño Cristales is located.

The site was effectively closed to tourists for several years because of guerrilla activity in the region along with concerns about the impact of unregulated tourist traffic. It was reopened to visitors in 2009, and today there are several Colombian Tourist Agencies that will fly travelers to La Macarena. From there, they must make their way to the river site on horseback (or donkeyback) and by foot as part of a guided tour. Visitors are not permitted to stay overnight or cook.

Swimming is permitted only in designated areas. Swimmers mustn't wear a sunscreen as to not destroy the fragile ecosystem.

For perfect photographs, check the weather forecast, because when it's cloudy, the sun rays do not illuminate the river so the colors are not that vivid. If there was no rain for a while, the water levels drop killing the fragile plants and turning the color from bright red to brownish.