The Central building is situated in the city centre, about 35km from the Airport.
A. To get there, after your arrival at the Athens International Airport, by METRO (subway):
The Airport is accessible via Metro blue line #3. Issue an 8 € ticket, which is valid for multiple trips with all means of transportation within 1 h and 30’. Trains depart every 30’ at XX:03, XX:33. In Syntagma station and after ~40’ travel and around XX:42 and XX:12 respectively, you have to change to red line 2, following the sign with direction to Ag. Antonios (Αγ. Αντώνιος). The next station Panepistimio (Πανεπιστήμιο) is your final destination. Proceed to exit Akademia (see next fig. --> Metro).
B. To get there, after your arrival at the Athens International Airport, by Suburban Railway:
In case that the Metro train just left or you don’t want to wait for 15’ – 20’, you can just get in to any (regardless the final destination) of the suburban train on the opposite side of the same platform with the same ticket. The trains depart at XX:11, XX:26 and XX:44. After 16’ distance, you are changing at Doukisis Plakentias (Δουκίσσης Πλακεντίας) station to metro blue line # 3 (Direction to Egaleo – same ticket).
Tip: For this change you just follow (for ~120m) the majority of the disembarked passengers, moving to the platform with direction to Egaleo (Αιγάλεω). You change in Syntagma and then the same as above in Metro case.
C. Maps to help you: