passages' total length) including statues carved from the rock salt at various times. In 1978 the Wieliczka Salt Mine was placed on the original UNESCO list of World Heritage Sites. The mine was on the List of World Heritage in Danger from 1989 to 1998. This was due to the threat of serious damage being done to the sculptures from humidity caused by artificial ventilation introducted in the later 19th century. A legend about Princess Kinga, associated with the Wieliczka mine, tells of a Hungarian princess about to be married to Bolesław V the Chaste, the Prince of Kraków. As part of her dowry, she asked her father, Béla IV of Hungary, for a lump of salt, since salt was prizeworthy in Poland. Her father King Béla took her to a salt mine in Máramaros. She threw her engagement ring from Bolesław in one of the shafts before leaving for Poland. On arriving in Kraków, she asked the miners to dig a deep pit until they come upon a rock. The people found a lump of salt in there and when they split it in two, discovered the princess's ring. Kinga had thus become the patron saint of salt miners in and around the Polish capital. During the Nazi occupation, several thousand Jews were transported from the forced labour camps in Plaszow and Mielec to the Wieliczka mine to work in the underground armament factory set up by the Germans in March and April 1944. The forced labour camp of the mine was established in St. Kinga Park and had about 1,700 prisoners. However, manufacturing never began as the Soviet offensive was nearing. Some of the machines and equipment were disassembled, including an electrical hoisting machine from the Regis Shaft, and transported to Liebenau in the Sudetes mountains. Part of the equipment was returned after the war, in autumn 1945. The Jews were transported to factories in Litomierzyce (Czech Republic) and Linz (Austria). The mine is one of Poland's official national Historic Monuments (Pomniki historii), as designated in the first round, 16 September 1994. Its listing is maintained by the National Heritage Board of Poland. In 2010 it was successfully proposed that the nearby historic Bochnia Salt Mine (Poland's oldest salt mine) be added to the list of UNESCO World Heritage sites. The two sister salt mines now appear together in the UNESCO list of World Heritage Sites as the