The Jet d'Eau is hard to miss. Rising 140 metres above Lake Geneva, it fires 500 litres of water per second at 200 kilometres per hour. That's enough, as one local guide cheerfully notes, to fill four baths every second. What most visitors don't know is that it began as an accident.

A pressure relief valve on a 19th-century hydraulic plant kept exploding, so engineers installed a rudimentary fountain to absorb the excess. It was 30 metres high and entirely functional. The public loved it, and in 1891 the monumental version was inaugurated in the bay.

VoiceMap's self-guided audio tours use the Jet d'Eau to trace Geneva's industrial ingenuity, connecting the fountain's hydraulic origins to the city's tradition of precision engineering, and revealing how its LED lighting has turned a water jet into a rotating calendar of humanitarian causes.