The Wieliczka Salt Mine in the town of Wieliczka, southern Poland, lies within the Kraków metropolitan area.
From Neolithic times, sodium chloride was produced there from the upwelling brine. The Wieliczka salt mine, excavated from the 13th century, produced table salt continuously until 2007, as one of the world's oldest operating salt mines. Throughout its history, the royal salt mine was operated by the Żupy Krakowskie company. (Wikipedia)