Most people arrive in Athens when they fly to Greece, so it is a perfect place to start your adventure. Athens is named after Athena, the goddess of wisdom and war. The city is a beautiful blend of ancient ruins, bustling shops, and modern buildings. Just try not to get run over by the zipping cars with no concern for traffic rules.
On your first day, just spend some time wandering around and touring the surroundings. One place to check out is the Plaka district, which contains the Temple of Olympian Zeus. You can also walk to the Olympic Stadium, the University of Athens, the theatre of Dionysus, the Statue of Lord Byron, Zappeio Hall, Hadrian's Arch, the National Garden, the Presidential Palace, the Temple of Hephaestus, the temple of Artemis, the Hellenic Parliament, and the several beautiful churches in Athens. Along the way, check out the small markets and gelato shops!
The second day in Athens is a full day of walking as well. First, I recommend visiting the Acropolis before too many tourists arrive. For this hike, remember to pack sunscreen and lots of water. At the top, there are water fountains with warm water and over-priced drink stands on the way down. Depending on the time of day, the line to the Acropolis can be extremely long, and it's always a steep hike to the top. At the top of the Acropolis you will find hundreds of tourists, the Parthenon and the Temple of Athena Nike, which used to harbor a gold statue of Athena; her wings were clipped so she would stay in Athens and protect the city. While some think the Acropolis is the highest point in Athens, there is one hill that is actually greater in height and provides a better view of the city; I will get to that later. After you've taken too many pictures at the Acropolis, the next stop is the Acropolis Museum. Here, you can cool off in the air-conditioning and view the original, preserved ruins of the Acropolis. You might be thinking, "Ugh, a museum...just what I wanted," but this museum even has an ancient underground civilization, which you can view through the clear glass floors. It is truly a once in a lifetime experience!
On the third day in Athens, visit any sites you didn't have time to explore in the previous days, purchase souvenirs, and enjoy the Greek cuisine. Athens is a perfect place to try the traditional Greek gyro, but there are also American options such as pizza or subs. Another fun activity is hiking to the highest point in Athens: Mount Lycabettus. A little cable car will take you to the top, but you will still have to do most of the walking up to that point. However, a little walking is a small price to pay for the impeccable view. Pictures just don't do it justice.
Overall, it requires about two to three days to explore Athens depending on your pace. As always, wear shoes that are comfortable and durable because there is a fair amount of walking. And also, don't forget to enjoy the views while you are taking all those pictures!