Dettifoss waterfall in northern Iceland...

is extraordinarily impressive and is about 100 meters (330 feet) wide and has a drop of 44 meters (144 feet). Located in Jökulsá á Fjöllum, a large canyon cut by several volcanically-generated outburst floods — jökulhlaups — during the middle Holocene.

Dettifoss on a snowy spring day. (Click image to enlarge.)