Athens is the major transportation hub of Greece. The city has the largest airport in Greece and the largest port in Greece, which is also the largest port in Mediterranean in containers transport and the largest passenger port in Europe. It is also a major national hub for Intercity (Ktel) and international buses as well as for domestic and international rail transport. Public transport is serviced by a variety of transportation means, forming the largest mass transit system of Greece. The Athens Mass Transit System consists of a large bus and trolleybus fleet, the city's Metro, a commuter rail service and a tram network, connecting the southern suburbs to the city centre.