Fjaðrárgljúfur is a massive canyon, 100 meters deep and 2 kilometers long, carved by the Fjaðrá river since the last ice age 9,000 years ago. It is theorized that the canyon was formed by the progressive erosion of the soil by the glacial waters accumulated in an upstream lake. At one point, the lake’s dam broke and the immense volume of water rushing out formed this beautiful valley.