The walls of the mine look like unpolished granite, and come in various shades of gray.
There is an underground lake in the mine, and it is part of the underground tour, which only covers 3.5 km (2.2 miles) of the 287 km long site.
378 steps on a wooden staircase will bring you to the 64 meter (210 feet) high level of the mine. An elevator will take you back to the surface after the tour is done.
