Paris isn’t Paris without the Seine River.
The 780-kilometer-long river winds through the City of Light, curving around the iconic Eiffel Tower. It hosts tourists marveling at the sights of the French capital and supports the centuries-old UNESCO-protected French bookstalls on its banks. The Seine is as integral to the Parisian experience as the Thames is to London.
Despite being renowned as the world’s most romantic river, its murky, sometimes odorous waters don’t immediately inspire such thoughts.
In recent months, the Seine has been preparing for a new role: a controversial centerpiece for the 2024 Paris Olympics, starting later this month.
French authorities aim to showcase the Seine at this global event, which offers a stage for both sporting talent and a display of soft power. Paris has announced plans to clean the river and open it for swimming for the first time in 100 years, although there have been occasional swims in the past. More unprecedented moves followed—the Olympic organizers announced that the Games’ opening ceremony would take place outside the stadium, on the Seine, raising security concerns. President Emmanuel Macron pledged to swim in the river to demonstrate its safety, following in the footsteps of former Paris mayor and President Jacques Chirac, who made a similar promise in 1990.
Beyond a bold spectacle, the Seine’s cleanup highlights the contemporary challenges of such massive undertakings, especially those of historical significance. Paris is hosting the Olympics for the first time in 100 years. Pierre de Coubertin, a Frenchman, revived the Games in the late 19th century, adding to their significance for Paris.
Despite the anticipation, the Seine has faced difficulties. With weeks before the Games and $1.5 billion spent on cleanup efforts, the river’s readiness for swimming remains uncertain. After a series of failed tests, water quality has started improving, according to the Paris mayor’s office.
“This positive development is due to the return of sunshine and warmth and the efforts made to improve the Seine’s water quality,” the office stated. However, wet weather could still affect the river’s condition before the Games begin.
In June, activists threatened to pollute the Seine, reflecting its critical yet sensitive role in the Olympics. Without the push from the Olympics, the cleanup might not have progressed as much, said Lindsay Krasnoff, a historian and global sports expert.
“The Seine plays a dualistic role between our ‘Emily in Paris’ postcard moments and the reality of being a living, working, breathing river,” Krasnoff said.
Last month, E. coli levels exceeded safety thresholds in tests by Eau de Paris, ironically just after International Olympic Committee executive Christophe Dubi expressed confidence in swimming in the Seine this summer.
The river is both the backdrop and a main character in the Paris Olympics, and its outcome could offer lessons for future hosts.
Efforts to clean the Seine aren’t new. Decades-long attempts have increased fish species from three in the 1970s to about 35 today.
However, reversing years of pollution is challenging. Many Parisian homes still have direct outlets to the river instead of wastewater pipes, requiring homeowners to bear the cost of changes.
Climate change also affects the Seine’s cleanup, said Jay Famiglietti, a sustainability and global water risk expert at Arizona State University. Heavy rainfall can overwhelm the sewer system, resulting in untreated water entering the Seine.
“Today, these events are occurring more frequently,” Famiglietti told Fortune. “Planning for the Paris Olympics might not have fully accounted for the increasing frequency of intense storms.”
Authorities have tried various measures, including a storage basin to prevent water from entering the river and degrading its quality.
Despite years of effort, anticipating climate change’s impact on such massive projects remains tricky.
“Do we have a 100 percent guarantee? No,” Pierre Rabadan, Paris’s deputy mayor overseeing Olympic plans, told the New York Times. “If it rains continuously for a week before the races, water quality—even with all the work done—probably won’t be excellent.”
Paris Olympics 2024 representatives didn’t respond to Fortune‘s request for comment.
Looking forward, Parisians remain unsure about swimming in the Seine, especially given its failed contamination tests. It’s unclear what will happen to Olympic events if the river fails safety standards. France’s Sports Minister Amelie Oudea-Castera said earlier this year that “there is no plan B” because some version of plan A involving the river’s cleanup will have to work.
Projects like the Seine’s can be hit or miss. Large-scale events have prompted urban beautification, like Shanghai Houtan Park for the 2010 World Expo, noted Jennifer Minner, a Cornell University professor specializing in the impact of mass events on host cities.
However, there are also failures—Rio de Janeiro failed to clean up Guanabara Bay for the 2016 Olympics. While the Seine’s fate is still uncertain, Paris sets an example for future Games.
“Mega-events like the Olympics and World Expos can catalyze or accelerate urban transformation,” Minner told Fortune. She said Paris could set a precedent for future Games by emphasizing urban ecology.
There’s also a lesson in Paris’s river cleanup: it requires more than a last-minute scramble.
“We’ve seen that rivers can be restored, but it takes a long-term commitment. It can’t be a political flip-flop,” Famiglietti said.
Paris still plans to open the Seine to the public next year. However, with possible government changes and the sports event cycle ending in August, it’s uncertain if cleaning the Seine will remain a priority.
The Seine project highlights the responsibilities of hosting a major event, beyond the glitz and glamor. Paris aims to make its Olympics the most sustainable yet, minimizing new venues and recycling water for sports events. Los Angeles plans to continue these efforts in 2028.
“The desire to redefine hosting the Olympic and Paralympic cycles given environmental and sustainability issues… that’s just the tip of the iceberg,” Krasnoff said.
