The Tellure mining park created a via ferrata in 2009 to introduce its visitors to miners' work since the Middle Ages and the Renaissance. The temperature underground is around 50° F (10° C) throughout the year. The rocky walls of Saint-Jean's vein contain numerous metal ores such as copper, silver, and lead. The subsoil of the Sainte-Marie-aux-Mines' region, where the park extends, holds more than 150 different mineralogical species. Some are rare varieties that are traded or sold every year during an international market.