We spent in Konstantinos' apartment 6 nights. Konstantinos is a great host, really helpful and easy to communicate with. He responded all of our mails and sms very quickly. The apartment is in a great location, near the metro station Thissio (2 minutes) and the most important attractions as well as the archaeological sites. It is very clean, comfortable and quiet despite being close to the pedestrian street lined with restaurants and cafes. The apartment has fully equipped kitchen. From the balcony you can see the Acropolis. The inside of the apartment looks exactly like the pictures.
There was nothing more that we could have asked for.
Highly recommended for stay in Athens.