Athens is a fantastic city for a pre cruise.
Parthenon, Acropolis Museum, Plaka, Temple of Zeus, Olympic Stadium, Syntagma Square, Agora are a start. Then, if you want to travel a bit, temple of poseidon and Delphi are great day trips. Even further, you can go to Corinth. I ended up doing a precruise in Athens three straight years. Athens has always been one of my favorite cities but my wife had never been. After three years, she had finally seen most of the sites.
If you want a driver recommendation, I can provide name and phone number for driver we used all three years. He has also been used by a number of friends.