The Athens Metro is considered the most convenient means of transport in Greece! It is fast, always on time and relatively cheap since a ticket costs €1.40 for seventy minutes. If you are a student or an elder you are even luckier since you pay just €0.60 ! It operates until 00.00 on Monday, Tuesday, Wednesday, Thursday and Sunday and on Friday and Saturday is open until 2.00 p.m. You can also buy the 3 day tourist ticket for all means of transport which costs €22 and includes airport transport, as well.
There are three metro lines:
The green one (Line 1): Runs between the stations of Piraeus (the central port) and Kifissia (a cozy Athenian suburb)
The red one (Line 2): Runs between Anthoupoli and Agia Marina
The blue one (Line 3): Runs between Elliniko and Doukissis Plakentias with an extension to the EleftheriosVenizelosAirport. If you want to go to the airport, you can buy an eight-euro ticket.
You will definitely need the metro during your stay in the country and you will need to ask people about the direction you need to go, the lines you have to use and the stops you have to get off at. After this course you will be able to perfectly communicate and reach all your destinations easily. So, go for it!