The Polish mine, which opened in the 13th century, operated until 2007, when it had to close due to flooding. It is more than 178 miles long and reaches more than 1,000 feet below the surface. Hidden in its twists and turns is a treasure trove carved right out of the rock salt.
This includes a statuary, three chapels, and a cathedral carved out of natural gray salt, dating back to the mine's early days and still occasionally worked on by contemporary artists. It's a site we'd dearly love to visit -- and, thanks to Street View, we can now virtually explore a small portion of the warrens.