Far beyond the humble kitchen condiment, salt—quite literally—has a history of great depth. One fascinating chapter of that history lies deep below the earth in Poland, where in the 13th century, salt was mined from a location like no other. The largest of these mines still exists today. Surreally, the underground mine comprises vast, decorated chambers, illuminated by chandeliers; cavernous halls with sublime saline lakes; and chapels carved right out of the living salt surroundings. The subterranean site is so otherworldly it has to be seen to be believed. The Wieliczka Salt Mine, near Krakow, plummets nine stories, 1,072 feet (approx. 327 meters), below ground level. Via 26 mine shafts accessed over seven centuries, some 2,500 unique chambers were carved out through salt excavations, linking corridors which span a massive 245 kilometers (152 miles). A UNESCO World Heritage site since 1978, the otherworldly underground mine has become a hotspot for tourists. “The corridors …