If you have ever visited Paris, you may be surprised that there is a second river that flows in Paris.

Most people knows that the river Seine flows in Paris. There is another river?
Nobody living has seen this river in Paris.

The Seine in Paris
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So, where is this famous second river?

The Bièvre

The name of the river is Bièvre.
It is long of 33 km. It has its source in the commune of Guyancourt and flows into thirteen other communes before entering in Paris through the 14th, 5th, 13th and 12th arrondissements of Paris and then flows into the Seine. One of the communes it flows in has almost the same name as the river: Bièvres.

The reason why nobody living has seen this river in Paris is that starting in the commune of Fresnes it is entirely underground, as it has been canalized under slabs and 5 km have disappeared under rubble and urbanization in Paris.

The name Bièvre come from the Gaulish word bibero, that gave the word bièvre in Old French, meaning "beaver". The word in modern French is "castor".
So, the Bièvre is the "Beaver River".

Old Map of the River Bièvre
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I have been living in Fresnes for several years, starting in 1996. For two years, I was working in Arcueil, another commune where the Bièvre flows, but I did not realize that there was a river along the route I was taking to go to school.

Historically the river was heavily industrialized with mills, which led to the straightening of the river. Tanneries, butcher shops and dye-makers were built along its banks, leading to serious pollution concerns. Starting in the 18th century, the river was gradually culverted. [Wikipedia]

Tanneries on the River Bièvre in Paris at the end of the XIX^th Century
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However, at the beginning of the XX^th century, there were still visible parts of the river.

The River Bièvre in Paris around 1900
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So, because the river Bièvre is now completely underground in Paris, do not look for the second river in the French capital!