Skjálfandafljót, one of largest rivers of northern Iceland, with its source in Vonarskarð and the glaciers Tungnafellsjökull and Vatnajökull, with tributaries from the Ódáðahraun lava field. Flows through Bárðardalur valley.
Many waterfalls, among them Aldeyjarfoss, Goðafoss and (near Kinnarfell) Barnafoss and Ullarfoss.