Neo-Byzantine architecture (also referred to as Byzantine Revival) was a revival movement, most frequently seen in religious, institutional and public buildings. It incorporates elements of the Byzantine style associated with Eastern and Orthodox Christian architecture dating from the 5th through 11th centuries, notably that of Constantinople (present-day Istanbul) and the Exarchate of Ravenna. Neo-Byzantine architecture emerged in the 1840s in Western Europe and peaked in the last quarter of the 19th century with the Sacré-Coeur Basilica in Paris, and with monumental works in the Russian Empire, and later Bulgaria. The Neo-Byzantine school was active in Yugoslavia in the interwar period. Russian Empire Sophia Cathedral in Pushkin (1782–1788) was the earliest and isolated experiment with Byzantine treatment of otherwise neoclassical structures. In 1830s Nicholas I of Russia promoted the so-called Russo-Byzantine style of churches designed by Konstantin Thon. Nicholas I despised true Byzantine art; Thon's style in fact had little common with it. Notably, Thon routinely replaced the circular Byzantine arch with a keel-shaped gable, and the hemispherical Byzantine dome with an onion dome; layout and structural scheme of his churches clearly belonged to neoclassical standard. True Byzantine art, popularized by Grigory Gagarin and David Grimm, was adopted by Alexander II of Russia as the de facto official style of the Orthodox Church. Byzantine architecture became a vehicle of Orthodox expansion on the frontiers of Empire (Congress Poland, Crimea, the Caucasus). However, few buildings were completed in the reign of Alexander II due to financial troubles. Alexander III changed state preference in favor of Russian Revival trend based on 16th-17th century Moscow and Yaroslavl tradition, yet Byzantine architecture remained a common choice, especially for large cathedrals. Neo-Byzantine cathedrals concentrated in the western provinces (Poland, Lithuania), the Army bases in Caucasus and Central Asia, the Cossack hosts and the industrial region in Urals around the city of Perm. Architects David Grimm and Vasily Kosyakov developed a unique national type of a single-dome Byzantine cathedral with four symmetrical pendentive apses that became de facto standard in 1880s-1890s. The reign of Nicholas II was notable for the architect's turn from this standard back to Hagia Sophia legacy, peaking in the Naval Cathedral in Kronstadt and Poti cathedral. These designs employed reinforced concrete that allowed very fast construction schedule; their interiors contained clear references to contemporary Art Nouveau yet the exteriors were a clear homage to medieval Constantinople. Russian Neo-Byzantine tradition was terminated by the