Caño Cristales, The River Of Five Colors, Serrania De La Macarena, Meta, Colombia

In the jungle of the Macarenia struggle for nutrients for the soil to populate various fungi that help break down the trunks of trees.
The small circular pits, -giant's kettle- that characterize the river bed have been opened by high hardness minerals. When one of these hard mineral fragments fall into one of the cavities, large or small, begins to brushing rotate with the cavity wall and increases the dimensions of the well.