Naso's place is truly a gem! The view is even better than the photos, the apartment is lovely, clean and in the best location for sightseeing and walking around Athens! The building and the area around the apartment are quite run down, so keep that in mind when booking but it shouldn't deter you! Monastiraki in general is quite a touristy busy area so you do need to keep an eye out but the apartment itself felt very safe. There is also a beautiful bar 2 floors above the apartment, it was a little loud at night (but if you want quiet nights, the centre of Athens is not the place to go).
Naso was available and communicated quickly and effectively, a really great host!
Overall, cannot recommend enough, everything is within walking distance, the apartment is outstanding and the night-life on the surrounding streets will truly make your Athens trip all the better!