A remote Colombian river that flows simultaneously in yellow, blue, green, black, and vivid red for several weeks each year — caused by an endemic aquatic plant called Macarenia clavigera blooming on the riverbed.
For most of the year, Caño Cristales looks like any other river in the Colombian Amazon basin. Then, between June and November, the riverbed turns red. The cause is Macarenia clavigera, an aquatic plant endemic to this single river system. For the bloom to occur, the conditions must be exact: enough water to keep the plants alive, but not so much that the flow blocks sunlight from reaching them. During the brief transition between wet and dry seasons, the plant produces its pigment — a vivid, saturated red. But the river does not just run red. The underlying limestone is pale. Tannins from the surrounding forest create yellow tones. Blue algae colonize other sections. On a single afternoon walk along a 100-meter stretch, you can see all five colors simultaneously. Colombians call it el río que escapó del paraíso — the river that escaped from paradise.