On our trip to Poland, we tried to visit as many of the Seven Wonders of Poland as we could, including Wawel Castle and the Main Square of Krakow. The Salt Mine has received over 40 million visitors and has salt deposits over 13 million years old. It took us 350 steps down into the mines, and a chilly 800 throughout the mines to tour to 20 different chambers, including the Chapel of St.Kinga, took us about 3 hours.