Hi eric,

I believe you can take the metro to Monastriaki (end of the line), here is a good site it has a metro map and other transportation info:

http://www.athensinfoguide.com/gettingaround.htm#5

I think you might miss the last metro though waiting for you luggage etc. (I think the last line 3 metro is at 22:30 or 12:55?? - double check).

Alternatively the X95 bus runs 24 hours/day from the airport to Syndagma and there is a taxi stand across the street from Syndagma square.
The bus is really easy to figure out. They pull up right outside the airport doors - anyone can point you in the right direction. Fare is 3.20E.

http://www.athensinfoguide.com/gettingaroundbus.htm

FYI: This website is also good for site info or anything else under the sun pertaining to Athens. You can also email them enquiries - they respond promptly.

Cheers,

Murphy

The Metro doesn't run that late. Take the airport bus to Syntagma Square. Walk directly downslope from the bus stop along Mitropoleos Street. You'll see Athinas Street to your right across from the Monastiraki Metro Station about 10 minutes walk from the bus stop. The Cecil is a few blocks up on the left.