Paris is the capital and most populous city in France. Since the 17th century, Paris has been one of Europe's major centres of finance, commerce, fashion, science, and the arts. 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. Paris is especially known for its museums and architectural landmarks: the Louvre was the most visited art museum in the world. Popular landmarks in the centre of the city include the Cathedral of Notre Dame de Paris and The Gothic royal chapel of Sainte-Chapelle, both on the Île de la Cité; the Eiffel Tower, constructed for the Paris Universal Exposition of 1889; the Grand Palais and Petit Palais, built for the Paris Universal Exposition of 1900; the Arc de Triomphe on the Champs-Élysées, and the Basilica of Sacré-Coeur on the hill of Montmartre. Paris received 23 million visitors in 2017, making it the world's top tourist destination. Paris has a typical Western European oceanic climate (Köppen climate classification: Cfb ) which is affected by the North Atlantic Current. The overall climate throughout the year is mild and moderately wet. Summer days are usually warm and pleasant with average temperatures between 15 and 25 °C (59 and 77 °F), and a fair amount of sunshine.