A truly superb place to stay in Athens. The location is very convenient, in a quiet but lively neighbourhood with lots of cafes, bars, and restaurants, close to the Acropolis and conveniently communicated with other parts of the city centre—essentially, most areas you will want to reach during a relatively short stay are within walking distance, as is the metro. The apartment itself is very clean, designed with a nice touch and attention to detail, and very well equipped. You won’t be disappointed, I wasn’t and I was expecting quite a lot.
(As a disclaimer, however, note that the Koukaki area has been quite heavy in Airbnb accommodation owing to its proximity to Athens’ main tourist attractions. This has led to a surge in rental rates, much to the detriment of local residents. Not very likely to affect the quality of your stay, but you may want to know that before you decide to book a place in the neighbourhood. If you do, you will do well to book this one.)