Dimmuborgir, or the Black Fortress, is a dramatic expanse of lava in the Lake Mývatn area.

The Dimmuborgir area consist of a massive, collapsed lava tube formed by a lava lake flowing in from a large eruption in the Þrengslaborgir and Lúdentsborgir crater row to the East, about 2300 years ago. At Dimmuborgir, the lava pooled over a small lake. As the lava flowed across the wet sod, the water of the marsh started to boil, the vapour rising through the lava forming lava pillars from drainpipe size up to several meters in diameters. As the lava continued flowing towards lower ground in the Mývatn area, the top crust collapsed, but the hollow pillars of solidified lava remained. The lava lake must have been at least 10 meters deep, as estimated by the tallest structures still standing.

Unfortunately the area has now turned into an overcrowded tourist trap compared to our first visit some 30 years ago!