The Bièvre, a legendary river that had a significant influence on the history of Paris, may return to the 5th and 13th arrondissements.This water source was polluted and overexploited by urbanisation and the many trades that set up along its banks from the 11th century, before being buried by the prefect Haussmann’s major sanitation works.Today, a project is under way to uncover it and offer residents a new urban landscape. But what might the terms and challenges be of such a renaissance for the Paris area?