Piraeus of social problems also emerged with the concentration of new populations in the suburbs of the old city, such as Nikaia, Keratsini, Drapetsona and Korydallos. The involvement of Greece in World War II came as a major setback to the city's progress. After the war, the city began its development once more, as damage to the port and the city were repaired and new additions took shape after 1955. Piraeus is now the third largest municipality in Greece; the city proper with its suburbs form the Piraeus urban area, which is incorporated in the Athens urban area, thus making Piraeus
Piraeus derby Piraeus derby The Piraeus derby, is an association football rivalry between Ethnikos Piraeus and Olympiacos, the 2 teams representing the city of Piraeus. Once a major derby, since Olympiakos' dominance the derby has lost importance over the years, however the rivalry still exists as the poaching of players and the ownership of the stadium still remain a point of contention. Although the importance of the derby has declined in football, the rivalry is still very much alive in other sports, especially water polo. Since the two clubs were established in the mid-1920s, Ethnikos' traditional local rival has been Olympiacos CFP,