Athens is the hub of the country's national railway system (OSE), connecting the capital with major cities across Greece and abroad (Istanbul, Sofia, Belgrade and Bucharest). The Port of Piraeus is the largest port in Greece and one of the largest in Europe. It is the largest container port in East Mediterranean Sea Basin. It is also the busiest passenger port in Europe and one of the largest passenger ports in the world. It connects Athens to the numerous Greek islands of the Aegean Sea, with ferries departing, while also serving the cruise ships that arrive. Rafina and Lavrio act as alternative ports of Athens, connects the city with numerous Greek islands of the Aegean Sea, Evia and Cesme in Turkey, while also serving the cruise ships that arrive.