Tucked deep in a valley in the heart of Telemark, the town of Rjukan has a history tied up in the waterfalls that tumble from its cliffs. Over a hundred years ago, tourists from Oslo flocked to this steep-walled valley to see the Rjukanfossen, then believed to be the tallest waterfall in the world. Free falling 104 meters into a rocky gorge, it kicked up a massive cloud of mist that gave the falls—and the town—its name. (In Norwegian, ‘rjukan’ means ‘smoking.’) Later, engineers came to harness the falls for hydroelectricity, channeling their energy through a series of power plants that came to embody a Norwegian ethic of shared progress through hard work. Captured by the Nazis in the 1940s, these plants were used to make heavy water, a key component of the Axis’s effort to build an atomic bomb—a plot thwarted only by a small team of local telemark-skiing saboteurs. Today, it’s still the water that draws people to Rjukan but for a new reason: to climb the frozen waterfalls that wreathe the valley through the long Norwegian winter.