The apartment is in a very nice building, totally renovated, rare for Athens. Everything is new and very clean, the studio is small but you have everything you need, a small kitchenette with tools, etc. I have been in many AirBnBs in Athens, but this was one of the best. The area looks a bit scary, but in 10 minutes walk (600m) you are in Monastiraki. There was also a free gym in the building!
Don't miss the Seychelles restaurant, as suggested by Sokol, no tourists, great food and a real Greek experience at less than 10 minutes walk from the apartment!