The city is a major rail, highway, and air-transport hub, served by the two international airports Paris-Charles de Gaulle and Paris-Orly. Opened in 1900, the city's subway system, the Paris Métro, serves 4.5 million passengers daily. Paris is the hub of the national road network, and is surrounded by three orbital roads: the Périphérique, the A86 motorway, and the Francilienne motorway in the outer suburbs.