The venue for the 2016 IEEE Symposium Series on Computational Intelligence is the Royal Olympic Hotel (Five-Star) . http://www.royalolympic.com/
Map and directions: http://www.royalolympic.com/athens_center_hotel
The Royal Olympic is not just one of the five star hotels in Athens.
There are many nice five star hotels in the centre of Athens.
There are few hotels in the world though, that have the privilege to be in front of important monuments. There are even fewer that offer their guests the opportunity to admire from the hotel, simultaneously, a number of Masterpieces.
From the Royal Olympic you have excellent view to The Temple of Zeus, The Acropolis, The Hadrian's Gate, The Marble Stadium and is infront of the National Garden.
Plaka (Old Town) is just across the road.
You can easily walk to all the above sites and if you wish to take the Underground, the Bus or the Tram they are all next to the Hotel.
You are exactly at the Centre of Historical Athens!