La Défense is a major business district just west of the city limits of Paris. It is part of the Paris Metropolitan Area in the Île-de-France region, located in the department Hauts-de-Seine spread across the commune of Courbevoie, as well as parts of Puteaux and Nanterre.
La Défense is Europe’s largest purpose-built business district with 560 hectares (1,400 acres) of area, 72 glass and steel buildings (of which 19 are completed skyscrapers), 180,000 daily workers, and 3,500,000 square metres (38,000,000 sq ft) of office space. Around its Grande Arche and esplanade (“le Parvis”), La Défense contains many of the Paris urban area’s tallest high-rises. (wiki)