Hallstatt has been a major site of human activity for over 7,000 years. The reason: salt. Salt has been harvested by humans since at least 6000 B.C., and likely much longer than that. The salt mine at Hallstatt has been active since at least 5000 B.C. through the Bronze age, Greeks, Romans, Middle Ages, and into the modern one.
Hallstatt, along with other salt mines, helped to make the Dachstein-Hallstattersee region of Austria extremely wealthy. As a method to move valuable salt brine, 400 years ago a pipeline made of 13,000 hollowed-out trees was created. The wooden pipeline remained in use until quite recently.