Rjukan

Norsk Hydro built this town from almost nothing in the 1910s and 1920s, because the Rjukan Falls, a single drop of 104 metres, could make the electricity that saltpeter production demanded. Vemork power station went up between 1907 and 1911 and was the largest in the world at the time; it is better known now for the wartime heavy water sabotage. UNESCO listed the town in 2015. Gaustatoppen stands directly to the south and blocks the low sun from September to March, so in 2013 mirrors were raised on the northern mountainside to throw daylight back down onto the square.