The Library-Museum is housed in the Palais Garnier in the Rotonde de l'Empereur, a pavilion on the west side of the theatre, which was originally designed to be the private entrance for Emperor Napoleon III.

[1] After the Emperor's death in 1873 and the proclamation of the French Third Republic in 1870, President Mac-Mahon refused to use this Pavilion as a private space for the head of state.

Expenses exceeded the receipts, and the government needed a strong man to run the establishment but was afraid that the archives would be sold to generate money.

Access to the library may be difficult at times (the entrance is through the main foyer of the opera house), and it is advisable to call ahead to confirm the hours when it is open.

[6] Today, the Library conserves around 600,000 documents related to the history of the Opéra and the Opéra-Comique, including about 100,000 books, 250,000 autograph letters, 16,000 scores, 30,000 libretti, 100,000 photographs, and 30,000 prints.

The modern museum has five rooms which display three centuries of the Paris Opera's history through paintings, costumes, drawings of scenery, and scale models of set designs.