Hector Guimard was a French architect known for his Art Nouveau style. He was influenced by Viollet-le-Duc's theories of structural rationalism early in his career as seen in his 1895 school Ecole du Sacre Couer which featured a simple geometric plan and structural expression of materials. After visiting Brussels and seeing Victor Horta's work, Guimard's style evolved to incorporate flowing organic forms and materials like iron, stone, and glass as seen in his iconic Castel Beranger apartment complex of 1894. Later works like his Paris metro entrances from 1899-1905 featured curving spidery designs in iron and glass that came to define the Art Nouveau style.