Ever since the mid-1800s, the incredible underground salt architecture of Wieliczka, Poland—which was recently featured on Gizmodo—has been a hot spot for international tourism, nowadays bringing in an estimated 1.2M people a year. It's no real mystery why people are drawn here: the tunnels and caverns, which served as a functional salt mine from the time the it opened in the 1200s until 2007, boasts some 124 miles of corridors across seven levels, with the deepest point dipping to 1,073 feet below ground. There's a full-scale cathedral—chandeliers and a salty replica of da Vinci's Last Supper included—plus underground lakes, chapels, galleries, and altars. In all, it totals some 2,000 chambers carved from rock salt.
The Wieliczka mine's salt cathedral, which includes crystalline chandeliers made from reconstituted rock salt, landed it on the original 1978 short list of UNESCO World Heritage Sites. Another strange fact: there's a wellness complex inside, as the pollutant-free air has become something of a Mecca for people with asthma or other respiratory problems.
· Buildings You Can Lick: 9 Spectacular Structures Made Out of Salt [Gizmodo]
· Wieliczka Salt Mine [Unesco World Heritage Center]