Dettifoss makes a noise you can feel in your sternum before you see anything. The waterfall on the Jökulsá á Fjöllum is forty-four metres high and about a hundred wide, and it carries more water than any other in Europe, a grey, thundering mass of glacial silt and ice melt that drops into a canyon of black basalt. In summer the flow can reach several hundred cubic metres per second, and the spray rises in clouds that catch rainbows on sunny days.
Getting here is half the adventure. The approach from the Ring Road to the west side is generally paved, while the eastern approach is gravel and rougher, so choose according to your bike and your nerves, and check the conditions before setting out. The surrounding landscape is a vast, barren plain of lava and black sand, almost lunar in its emptiness, with the wind scouring everything and the temperature dropping fast. Roads can be closed by snow well into early summer.
The landscape has the feel of another planet, and it was chosen as the opening scene of a science fiction film in 2012, set on a primeval Earth. The river that feeds the falls rises under the great Vatnajökull ice cap and carries its sediment northward to the sea, grinding through the plateau as it goes. A few kilometres upstream is a smaller fall, Selfoss, and downstream is the dramatic gorge of Hafragilsfoss, with its basalt columns.
Nature here is spare and strong. The vegetation is thin, mostly moss and hardy grasses, and the air carries a mineral smell from the spray. In early summer, pink-footed geese and other birds pass through, and the occasional Arctic fox shows itself on the ridges. The colours are dominated by black, grey and white, until a rainbow breaks them.
There are only basic facilities, and nothing in the way of shops, so Húsavík and the Mývatn area are the main places for supplies. Walk the path to the edge of the gorge, keep well back from the edge, and give yourself time to watch.