Surt's Cave — Surtshellir

The largest lava cave in Iceland was named for the fire giant of Norse myth — and later became the last refuge of a band of outlaws hunted down and slaughtered inside it.

Surtshellir, in the Hallmundarhraun lava field of West Iceland, is one of the longest lava tube caves in the country — a passage running for well over a kilometre beneath the surface, formed when the outer crust of a lava flow cooled and hardened while the molten rock beneath drained away. Its name comes from Surtr, the fire giant of Norse mythology who is prophesied to set the world ablaze at Ragnarök, wielding a flaming sword bright enough to outshine the sun. Early settlers, encountering a vast underground cavity carved by fire in the middle of a barren lava field, had an obvious candidate for its origin. The cave's darker chapter is historical rather than mythological, recorded in Landnámabók and other early sources: a band of outlaws — men exiled from society under Iceland's harsh legal code, for whom killing was not a crime once formally declared an outlaw — took shelter in Surtshellir's depths, using its size and isolation to raid nearby farms and vanish back underground. Farmers eventually organised an armed expedition, tracked the outlaws into the cave, and killed them there. Archaeological excavations in the twentieth century recovered animal bones, iron artefacts, and traces consistent with sustained human occupation deep in the cave system, lending physical support to the outlaw story. The cave remains open to visitors experienced enough to navigate lava tube terrain, though sections have partially collapsed since the medieval period. Icelanders continued to treat it as a place best avoided after dark well into the modern era — not from any residual fear of Surtr himself, but from a general sense that a cave with that particular history had earned its reputation twice over.