Rjukan sits in an east-west valley, flanked by mountains that block the sun from September to March. So the town has mounted three 56-square-foot reflectors on a ridge nearly 1,500 feet above; the mirrors track the sun and beam a 1,476-foot-long ellipse of noontime daylight onto Rjukan’s market square.

Believe it or not, the concept for Solspeil, or Sun Mirror, is a century old, from back when the town first sprang up to house hydropower plant workers. The plant’s founder, Sam Eyde, read about the idea in 1913 and dreamt of building it. He believed that sunlight would increase workers’ productivity.