Want to see major sites in Athens for about 3-4, hours . Best tour suggestions
Where do you plan to stay? In town or near the airport?
Arrive in Athens in AM
From where? When? 7AM vs 1130AM make a real difference.
Even if you stay at the Sofitel at the airport, if you arrive in the morning and have to be at the airport the next morning, that gives you a lot more than 3 or 4 hours of free time to see Athens.
We are staying at the Wyndham Dolce Atticus Rivera
And flight arrives at 10:30 am
Indeed, you didn't choose the most convenient place to spend a night and be able to go to Athens.
That being said, by taxi Athens center where the main sites are is about 1 hour from the hotel.
So, if after checking in at the hotel you are still in good shape, you can take a taxi to go to town and spend at least the afternoon there. This gives you time to eat something, go to the Acropolis and walk around Plaka before returning to the hotel by taxi.
Anyway you would need 2 or 3 full days to see the major sites, Don't expect to be able to see them in a few hours.
I did the Acropolis using the Rick Steves Audio tour in my headphones. My sister and I started climbing at 8:30 am and finished seeing it all about two hours later. Then we had a snack and walked to the Ancient Agora. This was in March so heat wasn't a problem. But the Acropolis Museum is top notch and has a lovely cafe so if you have time for two spots maybe see that instead.