Merkers Adventure Mines

Merkers Adventure Mines are a visitor attraction in Krayenberggemeinde in the Wartburgkreis district of Thuringia, Germany, owned and operated by K+S AG of Kassel. They lie near the village of Merkers. The mines have a long history of salt extraction, and hold the record for concealing large amounts of Nazi gold during World War II. A hundred tons of gold and many works of art presumed to be stolen were discovered by the liberating United States Army in 1945.

Source: Wikipedia