The Wieliczka Salt Mine, in operation from the 13th century until 2007, is a vast underground complex reaching depths of 327 meters. Over the centuries, miners carved incredible structures out of the rock salt, including dozens of statues, three chapels, and an entire cathedral. The Chapel of St. Kinga is the most famous; everything in it, from the altar to the intricate chandeliers, is made entirely of salt. The chandeliers use salt crystals that have been processed to be as clear as glass. Because salt is naturally antibacterial and the air in the mine is free of many pollutants, the mine also houses a private sanitarium for people with respiratory conditions. It is one of the original 12 sites inscribed on the first-ever UNESCO World Heritage list in 1978.