Þórsmörk Valley Highland Route (F249)

The F249 to Þórsmörk drops you into Iceland’s most famous river crossing gauntlet — multiple glacial torrents that have claimed more vehicles than any other route on the island. Beyond the Krossá River crossing lies Thor’s Forest, a birch woodland oasis wedged between Eyjafjallajökull and Mýrdalsjökull glaciers. The route cuts through black sand deserts and lava fields before reaching the Langidalur hut complex, where hikers stage for the Laugavegur trail.

This is expert-level river crossing territory — glacial runoff varies hourly, and what’s passable at dawn can be axle-deep by afternoon. Modified 4WDs with snorkels and winches are standard here, along with local guides who read water levels. Best tackled June through September when rivers run lowest, though even then you’re gambling with nature. The payoff is accessing Iceland’s most dramatic highland valley, where volcanism meets glaciation in raw, untamed beauty.