Wieliczka Salt Mine. Artwork dating from 1719 of the mining operations at the Wieliczka Salt Mine, as depicted by the German mining engineer and geologist Johann Gottfried Borlach (1687-1768). Both miners and horses are shown in this cutaway artwork, with inscriptions at upper left and lower right. The salt mine at Wieliczka, Poland, is one of the oldest in the world. It was started in the 13th century and is still in use in the 21st century. By the 19th century, vast underground caverns had been excavated to depths of several hundred metres, including statues sculpted out of the salt deposits. In 1978, the mine became a UNESCO World Heritage Site.