Konstantinos' house is located literally in the best part of Athens!! We got really surprised by the positive during our trip with that fact. The house is close to the main spots of Athens, being it day spots or nigh spots, however, the neighborhood itself is really calm and quiet!! Next to the house, there are plenty of restaurants where Athenian families usually have dinner and the streets get super cozy. The metro is really close too!
Regarding the house itself, it has the basics, don't expect luxury. The bathroom is modern and the rooms are good with spacious beds. The kitchen is not that great for cooking, but we didn't have the need since we had lunch and dinner always in restaurants. The A/C is marvelous and does wonders!!
Lastly, although you really can see the Acropolis, don't expect that romantic view, you just can see a tiny bit if you look at far left.