All the other reviews are correct! Athanasios's place is incredibly nice, stylish, spacious, and in a great location!! Right on top of Gazi (area with lots of restaurants, clubs, and bars) and the Kerameikos metro stop! I highly recommend taking the metro because it's really conveniently located (two blocks to the right when you come out the front door) and easy to navigate! But if you want to walk, it is only 1-2 miles from all the archeological sites and museums you will want to see!
Additionally, we loved the balcony, hammock, spacious couch, equipped kitchen, and washer! Athanasios was kind enough to arrange transport for us from the airport (which I would recommend because the apartment may be difficult for a cab to find if you don't know what to look for). But you can also take the metro to and from the airport!
Athanasios was also very quick to respond to any questions we had and provided some water and wine to get our vacation started! We would highly recommend this apartment to anyone who wants to truly experience Athens and would definitely return here if we ever get the chance to visit Athens again!!
My only note would be that if you are a light sleeper, you may need to bring ear plugs because the bedroom is the closest room to the street so you can sometimes hear the train and cars going by. But we were able to sleep just fine with ear plugs! Really loved the apartment overall!