The name Þórsmörk (Thor’s Forest) properly refers to the mountain ridge between the river Markarfljót to the north and the river Krossá to the south, but is commonly used to refer to a long valley, carved long ago out of the mountains by an outlet glacier and further smoothed and leveled by the river Krossá, which flows out of the glacier Mýrdalsjökul. Here is a map of the area, showing various hiking trails.
The valley is quite sheltered and this has created a microclimate that is warmer than the surrounding area, making it an oasis for various plants and shrubs. Several rivers need to be forded to get there, and while some of them might be passable for regular 2WD cars with high road clearance, others are not, especially the last two: Hvanná and Krossá. These rivers can only be crossed by 4WD jeeps, trucks or buses (or the huge tractor kept on hand to pull out those that get stuck – an entertaining sight for everyone except the unlucky driver).
On the way you pass several interesting places, including Stakkholtsgjá: a small, gorgeous river gorge well worth exploring (more of that in later posts). Click either image to enlarge.