Answer by taking a quote from the following article:

Charles-Edouard Jeanneret, known as Le Corbusier (French: [l@ koRby'zje]; 6 October 1887 - 27 August 1965), was a Swiss-French architect, designer, painter, urban planner, writer, and one of the pioneers of what is now called modern architecture. He was born in Switzerland and became a French citizen in 1930. His career spanned five decades and he designed buildings in Europe, Japan, India, and North and South America.

An important early work of Le Corbusier was the Esprit Nouveau Pavilion, built for the 1925 Paris International Exhibition of Modern Decorative and Industrial Arts, the event which later gave Art Deco its name. Le Corbusier built the pavilion in collaboration with Amedee Ozenfant and with his cousin Pierre Jeanneret. Le Corbusier and Ozenfant had broken with Cubism and formed the Purism movement in 1918 and in 1920 founded their journal L'Esprit Nouveau in 1920. In his new journal, Le Corbusier vividly denounced the decorative arts: "Decorative Art, as opposed to the machine phenomenon, is the final twitch of the old manual modes, a dying thing." To illustrate his ideas, he and Ozenfant decided to create small pavilion at the Exposition, representing his idea of the future urban housing unit. A house, he wrote, "is a cell within the body of a city. The cell is made up of the vital elements which are the mechanics of a house...Decorative art is antistandarizational. Our pavilion will contain only standard things created by industry in factories and mass produced, objects truly of the style of today...my pavilion will therefore be a cell extracted from a huge apartment building.". Le Corbusier and his collaborators were given a plot of land located behind the Grand Palais in the center of the Exposition. The plot was forested, and exhibitors could not cut down trees, so Le Corbusier built his pavilion with a tree in the center, emerging through a hole in the roof. The building was a stark white box with an interior terrace and square glass windows. The interior was decorated with a few cubist paintings and with a few pieces of mass-produced commercially available furniture, entirely different from the expensive, one-of-a-kind pieces in the other pavilions. The chief organizers of the Exposition were furious, and built a fence to partially hide the pavilion. Le Corbusier had to appeal to the Ministry of Fine Arts, which ordered that fence be taken down. Besides the furniture, the pavilion exhibited a model of his "Plan Voisin" his provocative plan for rebuilding a large part of the centre of Paris. He proposed to bulldoze a large area north of the Seine and replace the narrow streets, monuments and houses with giant sixty-story cruciform towers placed within an orthogonal street grid and park-like green space. His scheme was met with criticism and scorn from French politicians and industrialists, although they were favorable to the ideas of Taylorism and Fordism underlying his designs. The plan was never seriously considered, but it provoked discussion concerning how to deal with the overcrowded poor working-class neighborhoods of Paris, and it later saw partial realization in the housing developments built in the Paris suburbs in the 1950s and 1960s. The Pavilion was ridiculed by many critics, but Le Corbusier, undaunted, wrote: "Right now one thing is sure. 1925 marks the decisive turning point in the quarrel between the old and new. After 1925, the antique-lovers will have virtually ended their lives...Progress is achieved through experimentation; the decision will be awarded on the field of battle of the "new".

What was the Pavilion?
An important early work of Le Corbusier was the Esprit Nouveau Pavilion,