From Syntagma Square one can see Athens 2 major hills, eg. the summits's of the Acropolis at 512 feet and Mt. Lykavitos at 1000 feet. The Acropolis is site of the Parthenon and the current Acropolis Museum while Mt. Lykavitos is home to The Church of St. George and an out door theater plus scenic overlook/loverslane. Mt. Lykavitos translates to Mountain of Wolves as a Lycos is a wolf in Greek. Say 'Lee-Kav-ee-tos' if you want to pronounce it properly.
Both offer great views but being higher Mt. Lykavitos is superior and one of the frist places in Athens you should visit day or night. Its accessable 24/7 and has a restaurant, lovers lane and small arena where concerts and plays are held.
One can walk (its a hike!), taxi or take the funicular cable car to the top from the Kolonaki areas Plutarchou St. (see the map) The funicular and restaurant have their own bewildering hours.
These are Athens' center 2 major hills and central landmarks & orientation points. Get between them and you are in Constitution Sq. or Kolonaki or at least near enough to get your bearings.
In the Photo below one can easily see Mt. Lykavittos from Syntagma Square. Thats its sticking up over the foreign ministy building center.