The Second Empire refers to the reign of Napoleon III from 1852 to 1870. During that time, Paris underwent a building boom that included the construction of the Opera, designed by Charles Garnier, and an expansion of the Louvre (then a royal residence, not the museum it is today). The excitement that emanated from Paris flowed to England and the United States and can be seen in iconic public buildings like the Leeds Town Hall in England, Philadelphia City Hall, and the Concoran Gallery in Washington D.C. Each of these buildings is capped with the signature of the Second Empire--a mansard roof. The mansard roof was not designed during the Second Empire, but it became emblematic of the period. You can easily recognize a mansard roof by its steep and double slope (it is very tall but not domed). Homes also adopted the mansard roof because it allowed for maximum habitable space. Second Empire is part of the Victorian family of styles.