1.4 billion Euros were invested to clean up the Seine for the Olympic Games.
By the way, the money was spent to upgrade the local sewage systems and waste water plants. For over 100 years it was not allowed to swim in the Seine in Paris.
Source: https://www.zeit.de/wissen/umwelt/2024-07/oympische-spiele-paris-seine-schwimmen-wasserqualitaet
Photo: https://www.pexels.com/de-de/foto/stadt-eiffelturm-frankreich-wahrzeichen-20413635/