Dimmuborgir, which means "dark forts" in Icelandic, is an area of volcanic arches, pillars, caves and bridges along the east shore. The black lava formations are the result of a 2000 year old lava flow, and numerous trails lead through the area. Cracks in the ground here often hide deep and dangerous crevices; stay on the marked trails.
The site of a major volcanic eruption known as the Krafla Fires of 1975-1984. The various overlying lavafields give an interesting striped appearance to the area on a larger scale. Some areas of lavafields that are still steaming, and there are solfataras and various lava formations. Nearby about 500m is a large explosion crater called Víti which is the same name as the similar explosion crater at Askja. It is a fairly large site and worth about half a day to walk around. To find it, set out from Reykjahlið, in the direction of Egillsstaðir and turn left at the signed turn after about 8km. It is a further 7km, a little way beyond the geothermal power station.
The shores along the south side of the lake are home to many pseudocraters, formed during volcanic eruptions when lava flowed over wetlands, eventually resulting in steam eruptions and forming these medium-sized craters. There are a series of trails in the town of Skútustaðir that lead through these craters and provide further information about the geology behind these formations.
This 529m tall peak is accessible from a trailhead along the road, just south of the mountain. The trail runs along generally flat land to the back of the mountain, after which it takes a decidedly vertical turn and leads straight to the summit. The trail is tiring and footing on loose rock can be tough - plan about forty-five minutes to an hour for the ascent. Views from the top are tremendous, making this a very worthwhile trek.
hverfjall (hverfell) crater
This 2500 year old, nearly symmetrical tephra crater rises 463 meters high and is 1040 meters across. It is accessible via a trail that runs from Reykjahlíð to Dimmuborgir. Access to the bottom of the crater is not permitted in order to prevent erosion - please obey signs and remain on the marked paths.