From sewage and scum to swimming in ‘blue gold’: how Switzerland transformed its rivers

Bathers relaxing by Lake Geneva, Switzerland, at the Bains des Pâquis, a swimming area in the centre of the city. Photograph: Fabrice Coffrini/AFP/Getty Images

In the first days of spring, people flock to Lake Geneva’s broad, tree-lined promenade, their faces tilted towards the sun. Dior, Cartier and Rolex are among the high-end shopfronts overlooking the water. René Rottenberg, 75, has just finished his 400m swim through this upmarket urban jungle – a ritual he repeats up to five times a week, even in midwinter.

For the retired gynaecologist, being able to swim in the crystal-clear water is the greatest luxury. “It’s just so fun,” he says. “The place is beautiful.”