Fr. Jim Tucker of Dappled Things has a post on the salt mines at Wieliczka (near Krakow) in Poland. He also has a link to photos of the place.

I’ve visited Wieliczka when I was teaching an intensive Summer English Language course in Poland (1991 —“ 1993). The place is amazing.

It is not only a great historical monument and tourist site, it contains a sanitarium for people with asthma and other respiratory problems. The salt air microclimate in the lowest levels combined with the stable ambient temperature and pure air combine to create the perfect atmosphere for patients.

The carvings and chambers you see as part of the tour are amazing. The chapels and the main church are magnificent.

A pious tradition recalls that before St. Kinga (sometimes also referred to as Kunegunda) came from Hungary to Poland to marry the Polish king she threw a ring down a well. When she reached the site of Wieliczka she stopped for a water break. They drew water from a well and her ring was found there. She directed that a mine be dug there. Salt, which was a valuable commodity in that time, was found and the find added to the Polish coffers.

The actual history and a lot more information may be found (in English) at the official site of the Kopalnia Soli —žWieliczka—.

As I recall, the St. Kinga church is also dedicated to St. Barbara. They are the patrons of miners.