Otto Wagner (1841–1918) is one of the most significant figures of turn-of-the-century architecture. He was associated with the Viennese Secession, a group of artists and designers headed by Gustav Klimt that initiated a departure from the conservative style of the Viennese Künstlerhaus. Wagner's visionary approach, described as structural rationalism, pioneered the use of materials such as glass, steel, and especially aluminum to redefine Viennese structural identity.