• salt-mine = das Salzbergwerk
• salt mine [tech.] = das Salzbergwerk [Bergbau]http://www.atlasobscura.com/places/detroit-sa...
Some 1,200 feet beneath the streets of Detroit, under the north end of Allen Park, Dearborn's Rouge complex and most of Melvindale, runs 100 miles of subterranean roads over an area of more than 1,500 acres. It is the Detroit Salt Mine
and as a Detroit industry it is older then automobiles.http://www.salzwelten.at/en/hallstatt/saltmine/
On the trail of the "Man in Salt" in the oldest salt mine
in the world!http://whc.unesco.org/en/list/32
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.