The giant jagged lava field at Dimmuborgir (literally ‘Dark Castles’) is one of the most fascinating flows in the country. A series of nontaxing, colour-coded walking trails runs through the easily anthropomorphised landscape. The most popular path is the easy Church Circle (2.3km). Check with the visitor centre in Reykjahlíð or at the cafe at Dimmuborgir about free guided ranger walks in summer.
It’s commonly believed that Dimmuborgir's strange pillars and crags were created about 2000 years ago when a lake of lava from the Þrengslaborgir and Lúdentarborgir crater rows formed here, over marshland or a small lake. The water of the marsh started to boil, and steam jets rose through the molten lava and cooled it, creating the pillars. As the lava continued flowing towards lower ground, the hollow pillars of solidified lava remained.