Kinga (Kunegunda) was a daughter of Hungarian King Bela IV and niece of St. Elizabeth of Hungary. She married King Boleslaus V of Poland at sixteen.
According to the legend, when Polish king sent his envoys to take princess Kinga to Poland to marry a Polish king, her father wanted to show a royal generosity by giving gold and silver from his treasury to the Poles. Kinga asked him to give a salt instead, since Poles did have gold and silver but they did not have much needed salr. The king let Kinga to take as much Hungarian salt as she wanted, but Kinda had a premonition and she just dropped her engagement ring to the mine before going to Poland.
After Kinga's wedding in Krakow she went for a trip to a nearby town of Wieliczka and she ordered to dig a well. People who dig the well had to stop because they encountered a hard stone. She then ordered to lift up a chunk of the stone - it was a pure salt with Kinga's ring inside. In the place where Kinga asked to dig a well - huge deposits of pure salt were found. Therefore she became a patron of salt-miners.
Boleslaw, Kinga's husband had a nickname "Bashful" (in Polish: Wstydliwy) because he was very peaceful and shy. It is even rumored that his marriage with Kinga was never consummated. After her husband's death in 1279 Kinga became a nun in Franciscan tertiary, later he established the new noon order (Poor Clare and built a monastery for her nuns. Kinga founded many churches and hospitals, she ransomed Christians captured by the Turks, and served the poor and ill. Her cult was confirmed in 1690 (then she became a blessed Kinga). The feast day devoted to Kinga is celebrated on July 24. She attainted officially the sainthood in 1999 by John Paul II, Polish pope. Read more about the pope in the article Pope John Paul II - Pilgrimages to Poland.
Wieliczka Salt Mine was established in medieval times. It is a World Heritage Site, located 101 meters below the surface, it is over 50 meters long, 15 meters wide, 12 meters high. It receives up to a million visitors yearly. Please visit the Official Wieliczka website in English.
Wieliczka, contains at least two chapels and many sculptures devoted to Kinga. Wieliczka's salt mine is a beautiful place to visit if you would plan a trip to Krakow.
I recommend a book written by F. C. Anstruther, J. Sekalski, F. C. Anstrother (Editor), entitled: Old Polish Legends