Envisat image of Grande Terre, the main island of the French territory of New Caledonia. In addition to Grande Terre, New Caledonia is comprised of the Isle of Pines, the Loyalty Islands (visible in the image to the northeast), Walpole Island, and the Huon, Chesterfield and Belep groups (visible to the northwest). The main island is surrounded by an extensive barrier reef system — the second largest after Australia's Great Barrier Reef – that forms a lagoon, covering an area of around 24 000 sq km.