Athens International Airport

left luggage

http://www.pacifictravel.gr/baggage.html

Monasteraki Metro Station Locker Information

This is handy if you are traveling between the port and the airport, and want to spend a few hours or the day exploring the historical center. Do realize, however, that there are only a limited number of lockers and you will be restricted by the size as to how large a suitcase or bag you can store.