South of Brusio, in the Swiss Canton of Graubünden, the Bernina railway must change elevation without exceeding its specified maximum gradient of 7 percent. So engineers adopted the appealing expedient of a spiral viaduct, an arch bridge of nine spans that carries a train through 360 degrees with a grade gentle enough to ensure safety.

Opened in 1908, it was recognized as a UNESCO World Heritage Site in 2008.