Iwami Ginzan — UNESCO Silver Mine Heritage

Iwami Ginzan is the remains of Japan's biggest silver mine, which from 1526 to 1923 pulled enough silver out of these mountains to supply one-third of the world's total in the 16th-17th centuries. That silver funded Japan's trade with Europe and Asia—Portuguese and Dutch ships carried it west; Chinese merchants took it north. UNESCO listed the site in 2007, unusual for a mine because Iwami managed its forests sustainably (they needed timber for mine supports but didn't deforest the mountains). The site includes hand-dug tunnels (you can walk 273 meters into one), smelting ruins, the Omori town (preserved Edo-period mining settlement), and the port where silver got shipped. It's spread out—2 kilometers between tunnel and town, mostly uphill. Rent a bike or take the bus; don't try walking it in summer heat.