Карнавале
Despite the initial project, the City decided to move its municipal historical library into the building, the Bibliothèque Historique de la Ville de Paris, previously housed in the Hôtel Le Peletier de Saint-Fargeau, allowing the latter to be annexed to the Carnavalet Museum. Between 1955 and 1968, the building was restored and extended to finally house the library. The heritage site architects, , Jean Creuzot and André Vois first strengthened the "hôtel", which was in danger of collapsing, destroyed all the 19th-century additions in the courtyard and gardens, and restored the "hôtel to its" early-modern appearance, including the interior and its painted panellings. From 1964 onwards, a new wing was added to the south, which serves as a conservation area for the growing archival collections. The new construction was deliberately kept simple and austere to highlight the original and restored Renaissance "hôtel". Two more basement floors were also dug under the foundations.