Paris is a major railway, highway, and air-transport hub served by two international airports: Paris–Charles de Gaulle (the second-busiest airport in Europe) and Paris–Orly. Opened in 1900, the city's subway system, the Paris Métro, serves 5.23 million passengers daily, it is the second-busiest metro system in Europe after the Moscow Metro. Gare du Nord is the 24th-busiest railway station in the world and the busiest located outside Japan, with 262 million passengers in 2015.