Wieliczka and Bochnia Royal Salt Mines

These two mines include some amazing galleries turned into chapels, workshops, storehouses, etc. Statues and decorative elements sculpted into the rock salt can also be found in both mines

Wieliczka Salt Mine

 This postcard was sent by Miguel

The Wieliczka Salt Mine (Polish: Kopalnia soli Wieliczka), located in the town of Wieliczka in southern Poland, lies within the Krakówmetropolitan area. Opened in the 13th century, the mine produced table salt continuously until 2007, as one of the world's oldest salt mines in operation.

The mine is currently one of Poland's official national Historic Monuments (Pomniki historii), whose attractions include dozens of statues and four chapels carved out of the rock saltby the miners, as well as supplemental carvings made by contemporary artists. - in: wikipedia

Bochnia Salt Mine

This postcard was sent by Boguslaw

The beginnings of the Bochnia mine as an excavating plant date back to 1248. Being a royal facility, the mine generated a huge income.
The Bochnia Salt Mine is the greatest treasure of the Bochnia region. Thanks to the salt deposits, the town of Bochnia became one of the most important economic centres of Medieval Małopolska. With each passing century, the Salt Mine continued to leave a distinct mark on the history of the city, its urban development but also the history of business initiatives, and industrial and social development. It is here, in the Bochnia mines, that the process of innovating salt excavation methods gave rise to the introduction of then novel technical solutions.  - in: http://bochnia-mine.eu/okopalni/historia/