Hundreds of feet under Transylvania lurks a gaping hole where undulating layers of black, white, and gray wind along rocky subterranean walls. Millions of years ago, a sprawling sea once blanketed the region of Romania where this cavern now lies. But the water has long since dried up, leaving behind the mineral that gives the cave walls their stripes: salt.

This saline secret was a boon for the region and was mined for hundreds of years, starting as early as 1075. As miners extracted the mineral, they dug the magnificent cavern, expanding it until the mine, known as Salina Turda, closed in 1932. Now, the subterranean space has a fresh purpose, delighting visitors as an underground amusement park.

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