Greece 3 days before RS tour

We went to mykonos bef our tour. We flew aagean airlines, easy to walk around the island town, see windmills and relax.

And we chose Santorini for four days before meeting the tour in Athens. It's a beautiful island and we were happy to explore all it has to offer. We went in mid October so not very crowded.

You could go to the beach at Porto Rafti (close to the Athens airport). You could take the subway to Piraeus (Athens' port) for an afternoon. The ferry to Santorini is about 8 hours so I would fly if you decide on that island (other Cyclades are closer but still several hours away on the ferry).

With your time frame I would suggest either Aegina or Hydra with Aegina having far more to do and see. It's closer than Hydra. However, Hydra has one of Greece's prettiest waterfronts and towns but not much else if you are expecting archeological/historic sites and beaches. It is the only island I can think of that bans motorized vehicles. All transportation is done by donkey which will give you an idea of "old" Greece but Hydra is not "old Greece" by any means. It's now, popular with jet setters, day trippers and a great place to hang out, drink, eat and wander around.

Aegina on the other hand has a lovely main town with an impressive archeological site near by, one of the best preserved temple in Greece, abandoned Byzantine Village in the hills, ancient olive groves, seaside villages, hiking, and is closer to get to from the mainland.

You can do Aegina as a day trip leaving early morning and returning late day to Athens and have a night out or spend a night or two on Aegina for a nice Greek Island Experience.

Nothing wrong with Hydra but Aegina has more options.

Check the current tour itinerary? When we took this tour, we spent 2 nights and one entire day with nothing scheduled ("vacation from our vacation") on Hydra. The harbor is pretty and it's fun to relax in one of the small cafes and watch the local cats gather there, eagerly awaiting the arrival of the fishing boats. Yes, they received plenty of "rewards" for their patience!

If you can squeeze it in I highly recommend Meteora in Central Greece. May have to do an overnight but well worth it! I visited several islands when I went...felt one was like the other and if I could choose a favorite it'd be Mykonos. Have fun!

If you can squeeze it in I highly recommend Meteora in Central Greece. May have to do an overnight but well worth it! I visited several islands when I went...felt one was like the other and if I could choose a favorite it'd be Mykonos. Have fun!

Meteora would be an obvious choice. It's spectacular and would be very enjoyable for two nights.
Or, the island of (pick any; they're all incredible for their own reasons). If you're flying in to Athens, you might just get another plane out to an island that's farther away. If you'll be in town, you can easily get to the ferry ports. I would say any ferry ride greater than 5 hours in duration would be better flown but you can get to a lot of islands in 5 hours or less. Unfortunately, in early May you probably won't be doing much swimming which is a tragedy.