The city's main thoroughfare is the celebrated Nevsky Prospekt. On it are the high-spired admiralty building; the Winter Palace, built by Rastrelli; the Hermitage museum; and the Kazan Cathedral. Nearby on Senate (formerly Decembrists) Square are the huge domed Cathedral of St. Isaac (1858); Russia's Constitutional Court, in the Senate and Synod buildings; and the equestrian statue of Peter the Great, Falconet's masterpiece and the subject of Pushkin's poem "The Bronze Horsemen." The city's oldest building is the fortress of Peter and Paul (1703), which served as a political prison in imperial days. Among the baroque buildings of the early 18th cent. are the Alexander Nevsky monastery (1710), the Cathedral of Saint Peter and Saint Paul (1733), the Winter Palace (1762), and the Smolny convent (1764). Neoclassical buildings of the late 18th and early 19th cent. include the Academy of Arts (1772), the Marble Palace (1785), the Taurida Palace (1788), the Kazan Cathedral (1811), and the Exchange (1816). Among the city's educational institutions are the St. Petersburg State Univ. (est. 1804) and the St. Petersburg State Univ. of Economics and Finance. There are numerous theaters, museums, scientific and medical institutes, and libraries, including the 18th-century Maryinsky Theater (including a new ballet and opera house, opened 2013), the Saltykov-Shchedrin Public Library (1795) and the Academy of Sciences library. Outside the city are Pushkin, with the summer palaces of Catherine II and Alexander I, and the former imperial residences of Peterhof and Gatchina. A striking phenomenon of St. Petersburg is the prolonged twilight, or the "white nights," of June and July.