Paris (locally) is the capital and most populous city of France, with an administrative-limits area of 105 square kilometres (41 square miles) and a 2015 population of 2,229,621. The city is a commune and department, and the capital-heart of the 12,012 square kilometres (4,638 square miles) Île-de-France region (colloquially known as the 'Paris Region'), whose 12,142,802 2016 population represents roughly 18 percent of the population of France. By the 17th century Paris had become one of Europe's major centres of finance, commerce, fashion, science, and the arts, a position that it retains still today. The Paris Region had a GDP of €649.6 billion (US $763.4 billion) in 2014, accounting for 30.4 percent of the GDP of France. According to official estimates, the Paris Region has the fourth-highest GDP in the world and the largest regional GDP in the EU. The City of Paris' administrative limits form a horizontal oval centred on its historical-heart Île de la Cité island; this island is near the peak of an arc of Seine river that divides the city into southern Rive Gauche (Left Bank) and northern Rive Droite regions. Paris is but the core of a built-up area that extends well beyond its limits: commonly referred to as the agglomération Parisienne, and statistically as a unité urbaine (a measure of urban area), the Paris agglomeration's 10,601,122 2013 population makes it the largest urban area in the European Union. City-influenced commuter activity reaches well beyond even this in a statistical aire urbaine de Paris (a measure of metropolitan area), that had a 2013 population of 12,405,426, a number one-fifth the population of France, and one that makes it, after London, the second largest metropolitan area in the European Union. The 2016 Metropole of Grand Paris initiative, encompassing the City of Paris and its surrounding petite couronne department communes, or area covering 814 square kilometers and representing a population of 7 million, aims to improve city-suburb cooperation through a unique governing body. The city is a major rail, highway, and air-transport hub served by two international airports: Paris-Charles de Gaulle (the second busiest airport in Europe after London Heathrow Airport with 63.8 million passengers in 2014) and Paris-Orly. Opened in 1900, the city's subway system, the Paris Métro, serves 5.23 million passengers daily, and is the second busiest metro system in Europe after Moscow Metro. Paris' Gare du Nord is one of the ten busiest railway stations in the world, with 262 million passengers in 2015. Paris is especially known for its museums and architectural landmarks: its Louvre is one of the most visited art museums in the world. The Musée d'Orsay is noted for its collection of French Impressionist art, and its Pompidou-center Musée National d'Art Moderne has the largest collection of modern and contemporary art in Europe. In 2017, the European Commission ranked it as the most "Culturally Vibrant City" in the EU., and its central Seine River banks are classified as a UNESCO Heritage Site. Other notable monuments are: the Notre Dame Cathedral, the Île de la Cité Sainte-Chapelle church; the 1889 world exposition Grand Palais, Petit Palais, and Eiffel Tower; the Montmartre Basilica of Sacré-Cœur; the central Louvre palace and Tuileries Garden, and the Arc de Triomphe further along the Axe historique (Paris' historical axis) just to the west of there. Paris received 22.2 million visitors in 2015, making it one of the world's top tourist destinations, but the number of greater Paris visitors dropped by 11.5 percent following the terrorist attacks the following year. The association football club Paris Saint-Germain and the rugby union club Stade Français are based in Paris. The 80,000-seat Stade de France, built for the 1998 FIFA World Cup, is located just north of Paris in the neighbouring commune of Saint-Denis. Paris hosts the annual French Open Grand Slam tennis tournament on the red clay of Roland Garros. Paris hosted the Olympic Games in 1900, 1924 and will host the 2024 Summer Olympics. The 1938 and 1998 FIFA World Cups, the 2007 Rugby World Cup, and the 1960, 1984, and 2016 UEFA European Championships were also held in the city, and every July, the Tour de France bicycle race finishes in the city.