It might not sound like a top tourist attraction, but Turkmenistan’s Door to Hell is pretty fascinating. Officially called the Darvaza crater, it was caused by a Soviet oil rig drilling into a natural gas cavern in 1971 and has been burning ever since.

Take an off-the-beaten-track tour to visit while you still can, as it's been reported that the Turkmenistan president wants to extinguish the fire (natural gas is an important resource for the country).

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