Jökulsá á Fjöllum streams over the waterfalls Selfoss, Dettifoss, and Hafragilsfoss, the second of which is the most powerful waterfall in Europe, and through the canyon at Jökulsárgljúfur National Park, which was formed by the explosion of a volcano situated directly beneath the river.
It is located on the west bank of the glacial river Jökulsá á Fjöllum, and extends 30 km northwards from Dettifoss waterfall, covering 120 km².