Otto Koloman Wagner (German: [ˈɔtoː ˈvaːɡnɐ] (listen); 13 July 1841 – 11 April 1918) was an Austrian architect, furniture designer and urban planner. He was a leading member of the Vienna Secession movement of architecture, founded in 1897, and the broader Art Nouveau movement. Many of his works are found in his native city of Vienna, and illustrate the rapid evolution of architecture during the period. His early works were inspired by classical architecture. By mid-1890s, he had already designed several buildings in what became known as the Vienna Secession style. Beginning in 1898, with his designs of Vienna Metro stations, his style became floral and Art Nouveau, with decoration by Koloman Moser. His later works, 1906 until his death in 1918, had geometric forms and minimal ornament, clearly expressing their function. They are considered predecessors to modern architecture.
Wagner was born in 1841 in Penzing, a district in Vienna. He was the son of Suzanne (née von Helffenstorffer-Hueber) and Rudolf Simeon Wagner, a notary to the Royal Hungarian Court. He began his architectural studies in 1857 at the age of sixteen at the Vienna Polytechnic Institute. When he finished his studies there, in 1860 he traveled to Berlin and studied at the Royal Academy of Architecture under Carl Ferdinand Busse, a classicist and student of Karl Friedrich Schinkel, the leader of the German school of neoclassical and neo-Gothic architecture.  He returned to Vienna in 1861 and continued his architectural education at the Vienna Academy of Fine Arts, under August Sicard von von Sicardsburg and Edouard von der Nüll, who had designed the neoclassical Vienna State Opera and the architectural monuments along the Vienna Ringstraße. In 1862, at the age of 22, he joined the architectural firm of Ludwig von Förster, who studio had designed much of the new architecture along the Ringstraße. The first part of his career was devoted to the transformation of that boulevard into showcase of neo-Gothic, neo-Renassiance, and neoclassical styles. During this period, which lasted until about 1880, he described his own style as “a sort of free Renaissance”.
His first realized major project was an Orthodox Synagogue on Rumbach Street in Budapest. His design was selected in a competition held in 1868, when he was twenty-seven years old. The octagonal hall of the synagogue was concealed behind a four-story structure facing the street. The hall was filled with light from stained glass windows on the octagonal lantern above, and large circular windows in each of the eight bays. On the first floor above the ground floor was an octagonal gallery reserved for women. The facade was made of brick of different colors, and was decorated with minarets and towers with a Moorish appearance, while the interior featured colorful patterns of mosaic slender on the walls and highly decorated columns which supported arches over each of the bays. 
He began to develop his own philosophy of architecture, based the need for buildings to be, above all, functional. He continued to develop this idea throughout his career. In 1896, in his book Modern Architecture, he wrote, “only that which is practical can be beautiful”.
Facade of the Rumbach Street synagogue (1870-73)
Interior of the Rumbach Street synagogue, Budapest (1870–1873)
Ceramic ceiling decoration and stained glass of Rumbach Street synagogue