Haussmann style architecture was very regulated thus, the next period of architecture and city planning evoked creativity and boldness. Haussmann style was known for using Paris stone (a type of limestone) but Art-Nouveau style which lasted a short 20 years (1890-1910), was the mix of materials – iron, steel, metal, etc. Some of the most notorious examples of Art Nouveau architecture can be found in cities like Barcelona. One of the most notable architects of this time was Hector Guimard. French Architect, Hector Guimard designed a building (Castel Beranger) in 1898 that won most beautiful facade in Paris. Guimard is also responsible for designing cast-iron and glass metro entrances (like Abbesses- 18eme). More of his work can be found in the 16, 7 and 8 arrondissements. Although Art Nouveau was more of a decorative touch than it was a revolutionary style, it remains important because it was a deviation from the traditional form of Haussmann architecture.