The Hallen Salt Mine is the world's oldest mine open to visitors, in which everyone from the age of four and up can take part in a hunt for the hidden treasure, following the mysterious ancient miners' tunnels for several kilometers in the mysterious mountain, on the perfect day trip for families, groups or classes. This mine is a distinctive architectural masterpiece that has baffled history scholars, as it extends with a great length over a large area, unlike other mines whose small area was mainly kept secret!