Short day trip to Athens from airport hotel

Since you'll be staying overnight before your flight, consider booking a room in the city center. What sort of activities or sightseeing interests you? Athens offers much more than just the Acropolis, and there are plenty of options within walking distance of downtown. It's impossible to list them all.

Check the Athens official website:

https://www.thisisathens.org/

Thank you but we are booked into the hotel at the airport, I should have made that clear. Also we leave at 6:20 in the morning on Sunday.

Sounion. About 45 minutes from the airport.

This might seem off-topic for ending a trip to Greece, but just in case, there's a large mall (actually an outlet mall) next to the airport. Perhaps you'll have some Euros left to spend, and as they say on their website, it's the "before your flight home" experience.

I've never been there, just driven past it several times.

https://www.factoryoutlet.gr/en/katastimata/factory-outlet-aerodromiou/

On a completely different note, since there's nothing interesting to do or see in the immediate vicinity of the airport, you could spend part of the day on the coast, either in Artemi, Port Rafti, or the port of Rafina, which is Athens' second ferry port.

The advantage of Rafina is that you can easily find taxis to get back to the airport (there's also a bus).

Rafina Port:

https://maps.app.goo.gl/D7JzeLLdiBHwFM7i9

In all these places you'll find tavernas, bars, restaurants, and sometimes a beach. Plenty to spend a few pleasant hours.

Going to Cape Sounion, as Lewis suggests, could also be an option; it's further away than the places I mentioned. You'll need to find a taxi for the trip there and back.

Hope you are staying at the Sofitel - our flights often leave at 6 am and many of the nearby hotels say they offer a free shuttle - BUT not at 3:30-4 am !

Pat from Victoria -- the Hotel Avra DOES offer a free shuttle even in the wee hours... the only requirement is that, when you book a room, at the same time you also book ahead the exact hour you will need the shuttle service both from the airport AND back to the airport... so that the hotel can have drivers avaiilable.

What time do you get off the cruise? It would help to know just how much of the day you’ll have available.
As you are already booked to stay at the airport & if you do want to see more (there’s so much more to Athens than the Acropolis) it seems a waste of your time to go out to the airport then back into the city, use a service like this so you can start exploring straight away when you get off the cruise ship, they’ll get your bags from you (just keep with you what’s absolutely necessary for the day) & deliver them to you at the hotel at whatever time you specify,
https://www.baggagement.com/
We can make suggestions of what to see in Athens once we know your time available & what sort of things would be of interest to you.
Alternatively, if you go direct to the hotel you have already had some suitable suggestions.

Thank you to everyone who replied to my question! As it turned out we did not check into the Sofitel Athens Airport until 3 pm, and had to get up the next morning at 4 am to catch a 6:45 am flight. So we just repacked our suitcases, and had a nice dinner in the hotel.

For people who are now planning trips from N America to Greece, this is a cautionary tale --- try to find flights that do not depart before 9 or 10 AM ... so you can have a decent last-night finale, and not have to dress & leave at 4 or 5 am.

Sounion/Temple of Poseidon, especially for sunset.