The Plan Voisin is a solution for the center of Paris, drawn between 1922 and 1925 by Le Corbusier. The plan for 1925 seems to be a direct transposition of the diagram of Contemporary City for three million drawn in 1922. Included are buildings available in a regular orthogonal grid occupying a very important part of the right bank of the Seine. The space is highly structured with two new traffic arteries pierced through the city, one on the east-west, the other on a north-south. Their role is not limited to the organization of Paris, as were the advances of Haussmann: they pass through the fortifications and the suburban area. They have the ambition to link the capital to the four corners of the country, the major French and European cities. The crossroads at the intersection of these two avenues is the center of the plan, the center of the city in central France.

Le Corbusier opposed the idea of building a new administrative city in the periphery (that is La Defense) and proposes to build at the foot of Montmartre, opposite the island of the City's new command center that it considers necessary for the vitality of the country. The density of sky-scraper is 1,200 inhabitants to the acre. This figure is much higher than the average density of Paris in the heart of town (146 inhabitants to the acre) and of London (63) and of the over-crowded quarters of Paris (213), and of London (169). This great density shortens the distances of travelling and ensures rapid intercommunication.