Mines in the Karavanke mountains near Mezica (formerly Miess), which lies close to the border with Austria, north-west of Velenje, were worked from the 17th century, and were one of the principal sources of lead and zinc in the Habsburg Empire. The mines were celebrated as a source of wulfenite which contains both lead and molybdenum. Production reached a peak when the area was part of Yugoslavia in the years after the Second World War, when severe pollution was caused by fumes from the furnaces that smelted the ores, and the area was called Tal des Todes (death valley).
The mines and the smelter closed in the 1990s and a small part of the labyrinth of underground workings is open to the public. Visitors are taken on a train 3.5 km into the mine where there are displays illustrating the methods of extraction that were used there at different periods in the past. At the mine entrance are displays of photographs of the area and of tools and other equipment used in mining, together with a rich collection of geological specimens.