A short hop from Kraków, the Wieliczka Salt Mine hides an entire chapel carved hundreds of feet underground, where even the floor tiles, the altar reliefs, and the sparkling chandeliers are made from solid rock salt. Generations of miners shaped St. Kinga's Chapel by hand using ordinary mining tools.
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Wieliczka was one of the very first dozen places named a UNESCO World Heritage Site, in 1978, the same year Kraków's Old Town made the list.
Source: Wikipedia: Wieliczka Salt Mine