Iceland has some of the world's longest lava-tube caves, formed after volcanic eruptions when conduits of molten rock drain downhill. Lava pillars, mineral stalactites, ice candles, and snaking side passageways are among the intriguing formations within. Walking through these caves generally requires agility and sure-footedness but no specialized training or equipment, so virtuoso spelunkers tend to devote their energies elsewhere. Ice caves are also common in Iceland, but they're too dangerous to enter.
Among the many lava-tube caves worth seeking out are Raufarhólshellir, near Hveragerði in southwest Iceland; Surtshellir and Víðgelmir in west Iceland; and Lofthellir near Lake Mývatn.
If you plan to explore any caves on your own, bring a strong flashlight, warm clothing, and sturdy shoes. Helmets, knee pads, gloves, and headlamps are also advised, and caves with icy floors may require studded boots. The smartest procedure is always to seek out expert local advice beforehand.
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