Nestor is a wonderful responsive host, who really looked after us well during our stay. The apartment is exactly as described and is actually much bigger than expected. The outside of the building is a little rundown, but to be honest, this is true of most of Athens!
We do not consider ourselves "fit", but we ended up exploring all the main tourist sites, walking directly from the apartment. We had planned to use the subway which is about 5mins walk away, but actually enjoyed strolling (and eating lol) our way through the different city blocks and seeing the different communities.
If you are looking for a place to stay in Athens with a 5* host, add this property to your short list.