We had a wonderful time in Konstantinos' apartment! From the very start, Konstantinos was very kind and prompt in his communications and always available to answer questions. The apartment itself was well appointed and had everything we needed for a comfortable stay. Konstantinos' apartment is in a great part of town: just a short walk to Major archaeological sites and museums without being touristy at all. There are a number of great restaurants within walking distance, but we were delighted to find the most delicious Cretan taverna just around the corner. The only caveat is that there is a damp smell in the apartment which seems to be the result of mold in the bathroom-- entirely understandable given that it's hard for air to circulate in that space. Just something I keep in mind if you or anyone you're traveling with is sensitive to such things.
Overall, a wonderful place to stay in Athens!