The exhibition began its worldwide tour at the Institute of the Arab World in Paris in 2015, moving to the British Museum and then onto Zurich’s Rietberg Museum, which was the last stop in its European journey
The ancient Wieliczka salt mine, begun in the 13th century, is now a UNESCO World Heritage site.
In an open letter, the organisation criticises building work in the historic area, which is on the nomination list to become a World Heritage site