Places to visit in Athens are:

Parthenon on top of Acropolis Rock, Lycabetus Hill, the various museums, the National Garden, Plaka district with the traditional market Monastiraki.

Athens has also many museums as: 

New Acropolis Museum, National historical, Archaeological, Benaki, Cycladic Art, Byzantine, National gallery of art, Greek folk art, Music instruments

In Athens are also many theatres such as: 

Herodes Atticus, Dora Stratou, Theatre of Filopappos (in the summer), Megaron Concert Hall, National Opera ...