Dominating the lava fields on the eastern edge of Mývatn is the classic tephra ring Hverfjall (also called Hverfell). This near-symmetrical crater appeared 2700 years ago in a cataclysmic eruption. Rising 452m from the ground and stretching 1040m across, it is a massive and awe-inspiring landmark in Mývatn.
The crater is composed of loose gravel, but an easy track leads from the northwestern end (toilets here) to the summit and offers stunning views of the crater itself and the surrounding landscape. A path runs along the western rim of the crater to a lookout at the southern end before descending steeply towards Dimmuborgir.
Access the walking track via a signed gravel road – it's about 2.5km from the main road to the car park.