My husband and I stayed in Konstantinos's apartment for several days, and it gets our highest recommendation. One of those places where you immediately feel at home, despite being in the centre of Athens...
The pictures are an accurate reflection, although the apartment is bigger in real life. Two good bedrooms, a large living room, and modern kitchen and bathroom. There is a balcony down the side, where we enjoyed breakfast and drinks with a view of the Parthenon. Although the apartment is steps away from the pedestrian walkway, restaurants and the Parthenon, it is dead quiet at night, and we slept with the balcony door open (there are screens, which are rare in Greece!). The neighbourhood is completely safe...
The apartment itself is modern, spotless, and comfortable. It has been recently renovated, is light filled and arty, but is casual and comfortable . We routinely walked to the Monastiraki area, and into the Plaka in minutes. It is an interesting walk to the central food market and the National Archeological Museum.
I don't think that you can do better: great value for money, but fun, modern, clean and secure. We would go back in a heartbeat!