La Défense

From Wikipedia:

La Défence is a major business district of the Paris Metropolitan Area and of the Ile-de-France region, located in the commune of Courbevoie, and parts of Puteaux and Nanterre, just west of the city of Paris.
La Défense is Europe's largest purpose-built business district with 560 hectares (5.6 million square metres) area, 72 glass and steel buildings and skyscrapers, 180,000 daily workers, and 3.5 million square metres (37.7 million sq ft) of office space. Around its Grande Arche and esplanade ("le Parvis"), La Défense contains many of the Paris urban areas's tallest high-rises, and is home to no fewer than 1,500 corporate head offices, including those of 15 of the top 50 companies in the world.