Dimmuborgir

Dimmuborgir ("Dark Castles" or "Dark Cities") is an extensive field of irregular lava formations — towers, caves, arches, and pillars — formed around 2,300 years ago when a lava lake drained away while its surface crust was still partially molten, leaving the towers as the hollow remnants of lava that had cooled around escaping gas vents and rootless cones. The result is a landscape of twisted black rock formations, some standing over 20 metres tall, that early Icelandic settlers found unlike anywhere else on the island.

Icelandic folk tradition has long held that Dimmuborgir connects directly to Hell, and that the formations themselves are trolls and other supernatural beings caught outside at sunrise and turned to stone — a common motif in Icelandic folklore for trolls, who cannot survive daylight. The site is also said to be the winter home of the Yule Lads (Jólasveinar), thirteen mischievous troll-like figures who, in modern Icelandic Christmas tradition, descend from the mountains one by one in the thirteen days before Christmas to leave small gifts — or rotting potatoes for badly behaved children — in shoes left on windowsills, and their mother Grýla, a giantess said to come down from the mountains to eat children who misbehave. The area is a protected nature reserve, and marked trails guide visitors through the formations to limit damage to the fragile moss that covers much of the surrounding lava field.