I stay at the Pentelikon from time to time during my business travels. The hotel is in a very nice location, but a little bit far from the city center. The main problem with the hotel is that the quality of the rooms vary significantly. I still could not discover how many 'types' of rooms they have : some are very nice and well furnished, some old and stinky,... So, which room you sleep depends on your chance.. The dining facilities are also a bit weak but there are very nice restaurants around the hotel. My only advice is; check other 'newer' hotels in the Kifissia area before booking at the Pentelikon. The prices flactuate and you may be lucky to find the same price for a better hotel..