Tunnels under the border aren’t anything new but they’re usually about smuggling. I can think of several examples off the top of my head including tunnels between Mexico and the USA for drugs, Egypt and Gaza for basic goods, and the former East and West Berlin for people. Those are all interesting and I don’t wish to diminish their importance but my attention was drawn to a different border tunnel with a purpose completely unrelated to smuggling.
The story can be inferred from Salzburg, Austria. The city name translates literally into Salt (Salz) Castle (Burg). It sits along the Salzach River, further emphasizing salt. It doesn’t take an undue imagination to conclude that salt must have been a major source of wealth at one time, considered worthy of a fortress for protection. That is indeed the case. Deposits formed by an ancient evaporating sea have been mined in the vicinity of Salburg for at least the last 3,000 years.
Some of the salt mines are no longer active but they continue to exist today as museums. The Hallein mine is one of the more accessible and popular, with wooden slides and an underground lake. The mineral known at Halite was named after the Hallein mine. Most people probably know Halite by a more common designation, rock salt.
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Some of the major tunnels at Hallein date back to the 15th Century and portions were excavated even earlier. Austrian miners dug further and further underground into the hillsides as they followed the lucrative seam of salt. However ancient mineral deposits have no respect for the arbitrary nature of modern borders. The Austrians began digging within their own territory but the salt continued into Bavaria.
The nations came to a compromise. In 1829 they negotiated a treaty that allowed the mine to cross the underground boundary. In return, the mine would employ up to ninety Bavarian workers.
Photo Courtesy of Flickr under a creative commons license
Museum visitors today can actually cross the international boundary between Austria and Germany during their tour, a rare example of a legal underground border.