"The Phantom of the Opera" musical is based on a book about which French opera house?

"The Phantom of the Opera" (French: "Le Fantôme de l'Opéra") is a novel by French author Gaston Leroux. It was first published as a serial in "Le Gaulois" from 23 September 1909 to 8 January 1910, and was released in volume form in late March 1910 by Pierre Lafitte.

The setting of "The Phantom of the Opera" is the actual Paris opera house, the Palais Garnier.