From Athens International Airport Eleftherios Venizelos:
Tourists can take line three of the Metro into the centre of Athens. This will be the quickest and most efficient means of transport. This will cost about 6 Euros. Travel time is approximately 35 minutes to one hour. Trains usually run every 30 minutes from around 6 30 A.M to 11 30 P.M.
Visitors can also take a cab from right outside the Main terminal building. This is not advisable, however, since cab drivers stationed at the airport charge exorbitant rates ranging from about 20 to 30 Euros. Moreover, traffic jams mean it will take a very long time getting into the city.
Alternatively visitors can take the bus into city centre which will be inexpensive although time consuming. On the plus side buses operate all day and all night. Buses depart from outside the Main terminal building. Bus number 95 takes travelers from the airport to Syntagma, Omonia and then Piraeus. The ticket can cost from 1 Euro to about 4 Euros depending on the time of the day or night and the distance traveled.