ornament where every construction element was on display. The Werkbund organized a major exposition of modernist design in Cologne just a few weeks before the outbreak of the First World War in August 1914. For the 1914 Cologne exhibition, Bruno Taut built a revolutionary glass pavilion. Early American modernism (1890s–1914) Frank Lloyd Wright was a highly original and independent American architect who refused to be categorized in any one architectural movement. Like Le Corbusier and Ludwig Mies van der Rohe, he had no formal architectural training. In 1887–93 he worked in the Chicago office of Louis Sullivan, who pioneered the first tall steel-frame office buildings in Chicago, and who famously stated "form follows function". Wright set out to break all the traditional rules. He was particularly famous for his Prairie Houses, including the Winslow House in River Forest, Illinois (1893–94); Arthur Heurtley House (1902) and Robie House (1909); sprawling, geometric residences without decoration, with strong horizontal lines which seemed to grow out of the earth, and which echoed the wide flat spaces of the American prairie. His Larkin Building (1904–1906) in Buffalo, New York, Unity Temple (1905) in Oak Park, Illinois and Unity Temple had highly original forms and no connection with historical precedents. Early skyscrapers At the end of the 19th century, the first skyscrapers began to appear in the United States. They were a response to the shortage of land and high cost of real estate in the center of the fast-growing American cities, and the availability of new technologies, including fireproof steel frames and improvements in the safety elevator invented by Elisha Otis in 1852. The first steel-framed "skyscraper", The Home Insurance Building in Chicago, was ten stories high. It was designed by William Le Baron Jenney in 1883, and was briefly the tallest building in the world. Louis Sullivan built another monumental new structure, the Carson, Pirie, Scott and Company Building, in the heart of Chicago in 1904–06. While these buildings were revolutionary in their steel frames and height, their decoration was borrowed from Neo-Renaissance, Neo-Gothic and Beaux-Arts architecture. The Woolworth Building, designed by Cass Gilbert, was completed in 1912, and was the tallest building in the world until the completion of the Chrysler Building in 1929. The structure was purely modern, but its exterior was decorated with Neo-Gothic ornament, complete with decorative buttresses, arches and spires, which caused it to be nicknamed the "Cathedral of