Þjórsá is Iceland‘s longest river at 230 kilometers. It is in the southern region of the island. Þjórsá is a glacier river has its source on the glacier Hofsjökull. It flows out through narrow gorges in the highlands of Iceland. Further downstream, another river, the Tungnaá, flows into it, before it enters the lowlands. There it passes the valley of Þjórsárdalur (Thjorsardalur) where the historical farm of Stöng is located.