2 days in Athens were nice and comfortable.
We stayed at TwentyOne Hotel, which is conveniently located in Kifissia suburb, a residential upper class area of Athens.
Its leafy streets and historic square play host to the Greek headquarters of a wide range of major companies. Kifissia is only 10 minutes away from Maroussi business centre, 20 minutes train ride from the centre of Athens or 30 minutes by car from both Airport and city centre.
TwentyOne is a modern city hotel in Kifissia, one of the most affluent northern suburbs of Athens.
A creation idea of “Deca Architects” and Alexandros Vaitsos, guests can experience the combination of design, functionality, and comfort with an emphasis on personalized services.
What to add – good staff, conditions and the Spirit of Greece!!!

I stayed last year only for one night. It was very cool hotel but too modern for my taste as the weird bird on the ceiling freaked me out and couldn't enjoy my sleep. The toilet also made me feel a bit akward as my partner could see me every time I got in. Sounds funny but not so. May be I received the wrong room as, as much as I know the hotel provides super rooms with many themes. I would stay again in the future...but in a better room and better rate!

Hotel is absolutely OK, funny rooms (if you get the one with a window in the roof, you sleep looking at the stars...) Handicap: it got a little too worm even though the A/C was on. Breakfast was very good. The Restaurant 21 was fantastic ! One is ovbiously far away from the center. reception should have more info for tourists and give a bit more assistance in this respect.

Very comfortable rooms with good working area and ultrafast free Wi-Fi. Located in the "posh area" of Athens, far away from the old town and tourist attractions. Lot's of trendy restaurants and coffee shops in the neighbourhood. Most of the stores are very upmarket. About 25min taxi to the Airport (40mins in rush hour traffic). Reception not very friendly or particulary helpful. I paid € 150/night including very basic breakfast. There are more price worthy hotels in Athens. All in all, not a super nice hotel, even though the rooms are spacious, clean and good to work in.