We had a great experience at Costa's !
The flat was very well located, close to Thissio metro stop and several historical sites. The neighborhood is nice and Monastiraki and Psyrri are just a few minutes away.
Costa was very reactive in answering to the booking and made sure he could meet us in person at the apartment at the time of our arrival. He had everything ready and gave us with welcome advice on places to go out and eat. He also made sure we were okay during CoVid-19 curfew.
The apartment itself is spacious and was very clean. It has a very nice little patio where we had dinner and breakfast ; which is nice considering the flat is situated below street level and is otherwise a little dark. The bathroom is spotless and has a big bathtub. The kitchen is cooking-friendly and had good utilities. The doorlock is very safe and the building secure. The street is very quiet, as is the building.
All in all great host and a great place. We stayed at three different places in Athens that week and Costa's was the best of the three. We'd definitely recommend it and would book again!