The early mines shut down in the 1540s when silver flooding in from Spanish Latin America crashed prices across Europe. Recovery came decades later, driven by Chinese demand for currency as Portuguese traders established Macau in 1555 and commerce with the Far East intensified. When Admiral Ove Gjedde returned from establishing a Danish trading outpost at Trankebar on India's Coromandel Coast in 1622, King Christian IV redirected him to Norway to revive the mining industry. Gjedde restarted silver extraction in 1623, and the following year the king himself visited, founded the town of Kongsberg, and established the operation by royal charter as Kongsberg Soelvverk. A remote Norwegian hillside had become entangled with the global currents of colonial trade.

At its peak in the 1770s, over 4,000 workers labored across more than 80 mine sites, making Kongsberg the largest pre-industrial workplace in Norway. The operation contributed over ten percent of the gross national product of the Danish-Norwegian union -- a staggering figure for a single enterprise. The King's Mine, the largest and richest shaft, eventually reached more than 1,000 meters in depth. Significant new ore discoveries in the 1830s and 1860s extended the operation's life, and across its full 335-year history, more than 450,000 man-years of labor produced over 1.3 million kilograms of silver. The mines finally closed in 1957, but by then they had shaped everything about the town above them.

Today the Norwegian Mining Museum at Kongsberg offers visitors something few museums can: the chance to board a mining train and ride 2,300 meters through the Christian VII Adit into the mountain itself. The bottom of the mine sits 1,070 meters below the surface -- 560 meters below sea level. The space now called the Banquet Hall of the King's Mine began its life in 1943 as an emergency storage vault for the National Archives of Norway, built to hold 2,000 shelf-meters of documents and books safe from wartime threats. Around 40,000 visitors make the underground journey each year, and the tour includes a working man engine, the mechanical lift system that once carried exhausted miners back to daylight.

From above, the landscape around Kongsberg reveals little of the labyrinth below. The forested hills of Buskerud county roll gently toward the Numedalslaagen river, and the town itself sits in a valley with a quiet, prosperous feel. But for three centuries, this was one of the most important industrial sites in Scandinavia -- a place where the geological accident of silver-bearing rock intersected with the ambitions of Danish-Norwegian kings, the rhythms of global commodity markets, and the labor of tens of thousands of workers. The silver is gone, but the tunnels remain, carrying visitors into a darkness that once produced a nation's wealth.