Second Empire style, also known as the Napoleon III style, is a highly eclectic style of architecture and decorative arts, which uses elements of many different historical styles, and also made innovative use of modern materials, such as iron frameworks and glass skylights. It flourished in the Second French Empire during the reign of Emperor Napoleon III (1852–1870) and had an important influence on architecture and decoration in the rest of Europe and North America. Major examples of the style include the Opéra Garnier (1862–1871) in Paris by Charles Garnier, the Bibliothèque nationale de France, the Church of Saint Augustine (1860–1871), and the Philadelphia City Hall (1871–1901). The architectural style was closely connected with Haussmann's renovation of Paris carried out during the Second Empire; the new buildings, such as the Opéra, were intended as the focal points of the new boulevards.

The Palais Garnier, also known as Opéra Garnier, is a historic 1,979-seat opera house at the Place de l'Opéra in the 9th arrondissement of Paris, France. It was built for the Paris Opera from 1861 to 1875 at the behest of Emperor Napoleon III. Initially referred to as le nouvel Opéra de Paris, it soon became known as the Palais Garnier, "in acknowledgment of its extraordinary opulence" and the architect Charles Garnier's plans and designs, which are representative of the Napoleon III style. It was the primary theatre of the Paris Opera and its associated Paris Opera Ballet until 1989, when a new opera house, the Opéra Bastille, opened at the Place de la Bastille. The company now uses the Palais Garnier mainly for ballet. The theatre has been a monument historique of France since 1923.