An eerie world where everything has been carved from salt blocks, the Wieliczka Salt Mine (Kopalnia Soli) is made up of a labyrinth of tunnels, the deepest of which lies 1,075 feet (327 meters) underground. The ancient UNESCO World Heritage site is a major part of Poland's salt mining history, one of the country's most popular attractions, and one of the world's oldest salt mines, having produced table salt from the 13th century until 2007.