The Carnavalet Museum is dedicated to the history of the city. The museum occupies two neighboring mansions : the Hôtel Carnavalet and the former Hôtel Le Peletier de Saint Fargeau. On the advice of Baron Haussmann, the civil servant who transformed Paris in the latter half of the 19th century, the Hôtel Carnavalet was purchased by the Municipal Council of Paris in 1866 ; it was opened to the public in 1880. By the latter part of the 20th century, the museum was bursting at the seams. The Hôtel Le Peletier de Saint Fargeau was annexed to the Carnavalet and opened to the public in 1989.
Source : Wikipedia contributors, "Musée Carnavalet"