Even if the flat were ordinary, the views from the terrace across to the Acropolis would be worth it. The flat is not ordinary. It is small but so stylishly designed that it feels big with plenty of lovely touches.
It’s near Monastiraki from where you can take the metro to most places. There are restaurants outside your door. I’ve been to Athens many times but if I have to go again, it won’t be to a hotel.