The Wieliczka and Bochnia Royal Salt Mines illustrate the historic stages of the development of mining techniques in Europe from the 13th to the 20th centuries: both mines have hundreds of kilometers of galleries with works of art, underground chapels and statues sculpted in the salt, making a fascinating pilgrimage into the past. The mines were administratively and technically run by Wieliczka Saltworks Castle, which dates from the medieval period and has been rebuilt several times in the course of its history.