Fjaðrárgljúfur is a canyon in south east Iceland which is up to 100 m deep and about 2 kilometres long, with the Fjaðrá river flowing through it. It is located near the Ring Road, not far from the village of Kirkjubæjarklaustur.
The canyon was created by progressive erosion by flowing water from glaciers through the rocks and palagonite over millennia.[Source]