Been to Athens already

Any suggestions on what to do on our return visit? We have already seen all the major sites.

Are you sure you've seen all the sites in Athens? I've spent a day or two there nearly every year and there are still things I haven't gotten to...

What are you interested in?

Things near Athens worth a daytrip: Corinth, Eleusis, Sounion, Mycenae, Epidaurus, Nafplion. Delphi can be done in a long day but better if you have time for an overnight there.

We did all the major attractions, Parthenon, Acropolis, colosseum, the Agora Market, changing of the guard at the palace etc. it was a long tour day but wonderful. I think I'm looking for something off the beaten path.

If this is a port day, consider a private driver who can take you around outside Athens. Depending on timing, you could probably do Corinth and Eleusis, or Mycenae and Epidavros (although they are closer to Nafplion port).

What do you mean by "off the beaten path"? Athens has a number of smaller but very good museums that many people don't visit, including the Benaki Museum and the Museum of Cycladic Art. (It's not clear to me from your answer whether you've already been to the Acropolis Museum [the new one] and the National Archaeological Museum -- if you haven't, I'd put them high on your list.)

We did Athens in 2013 and again as an overnight in 2016.

During our first visit, we hit up all the "major attractions" but it was kind of disorganized because we didn't plan the day very well.

While we did repeat a few things during our second visit, here a few "non-standard" things we did that may help with some ideas.

We walked to the Central Market. Glad we went but I wouldn't characterize it as really geared towards tourists though. Along the way, we bought some spices from a vendor. It's a fairly easy walk.

We also strolled the Kolonaki neighbourhood which is kind of NE of Syntagma Square. It's a nice area with shops and cafes within walking distance of the core tourist areas.

The morning after our overnighter, we walked the waterfront area in Piraeus. We jumped on the express bus (X80) which drives fairly close to the southern waterfront area before heading northeast to Athens. We hopped off just before the second marina area and walked along the waterfront back to the port. Some areas were a lot more pedestrian friendly than others. Along the route, there's quite a few nice places to eat. We ended up eating at Margaro which has a simple menu but was affordable and delicious. Overall, we quite enjoyed this walk.

Maybe a trip to one of the islands? The ferries are very close to where the cruise ships dock. You can walk or take a cab (depending on how far out you are docked) to the ferry dock and buy your tickets at the docks. It's near the metro stop and bus stop.

Look into Aegina or Hydra. They have frequent departures. Aegina is about 45 mins and Hydra is about 1 hour each way (on fast ferry) so that gives you a few hours to explore the villages on the island.

Thanks for the suggestions, I'll look into all of them.