Rainbov River or Caño Cristales is a Colombian river located in the Serrania de la Macarena province of Meta. It's a tributary of the Guayabero River. The river is commonly called the "River of Five Colors" or the "Liquid Rainbow," and is even referred to as the most beautiful river in the world due to its striking colors. The bed of the river from the end of July through November is variously colored yellow, green, blue, black, and especially red, the last caused by Macarenia clavigera plants (family Podostemaceae) on the bottom of the river.
The quartzite rocks of the Serrania de la Macarena tableland formed approximately 1.2 billion years ago. They are a western extension of the Guiana Shield of Venezuela.
Caño Cristales is a fast river with many rapids and waterfalls. Often in the bed have formed small circular pits - giant's kettles, which have been formed by pebbles or chunks of harder rocks. Once one of these harder rock fragments falls into one of the cavities, it is rotated by the water current and begins to carve at the cavity wall and increases the dimensions of the pit
The Serranía de la Macarena is located on the border of three large ecosystems, each of them with high diversity of flora and fauna: the Andes, the Eastern Llanos, and the Amazon rain-forest. Plant and animal life are struggling with the lack of nutrients on the solid rock surface of the tableland and have developed diverse adaptations. The representative biome of the Serranía de La Macarena is the hydrophytic rainforest: hot, warm, and cold. The tableland is home to about 420 species of birds, 10 species of amphibians, 43 species of reptiles, and 69 primates.
Caño Cristales river has a wide variety of aquatic plants. The water of the river is extremely clear due to the lack of nutrients and small particles. Almost unique is the bright red - pink coloration of riverbed after the rainy period in the end of July - November. This color is caused by great quantities of endemic plant species Macarenia clavígera. This plant is found in some more local rivers, such as the Caño Siete Machos. These red plants adhere tightly to rocks in places where the river has faster current.