Opposite Square Louvois, the Bibliothèque nationale de France—founded in 1537—houses 22 million specialized items at its historic site, including manuscripts, prints, photographs, maps, musical scores, coins, and antiquities. The buildings form a remarkable heritage complex, developed between the 17th and 19th centuries and restored from 2011 to 2023. A visit reveals the Galerie Mazarine by François Mansart (1645), the Salle Labrouste (1854)—a masterpiece of metal architecture—and the Salle Ovale by Jean-Louis Pascal (1897). The BnF Museum displays treasures from antiquity and the Renaissance, such as the Throne of Dagobert, the chess set known as "Charlemagne's," and the Berthouville Treasure, alongside medals, globes, engravings, photographs, and original manuscripts by authors such as Hugo, Flaubert, and Proust.