10 days in Greece this October

Nafplio, for itself and as a base for Mycenae and Epidavrus. Delphi for itself.

Have you considered sleeping one night on the island Hydra which is a doable day trip from Athens? There's also Nafplio, which you can take a two hour bus ride from Athens to get to or hire a driver which will take one hour.
I wouldn't spend more than three nights in Santorini. You can take an overnight boat from there and sleep in a cabin and go to Rhodes. If you have a bit more time you may want to get off on Symi island and sleep there one night before going to Rhodes.

In mid-October 2019 (the end of tourist season), I took the ferry from Santorini to Naxos. While Santorini was still pretty crowded with overnight tourists and 2-4 cruise ships a day, Naxos was the opposite. Unlike Santorini, sunsets were not dramatic, but watching a pretty sunset alone on the beach or from the balcony overlook was much more enjoyable than jostling for a viewing place. Excellent restaurants were still open, no reservations needed. There were still daily tours to other parts of the island, everything was easy walking distance, including from the ferry port to the town center (5 minutes), the airport was a 5 minute drive away. There are lovely beaches just a few minutes away by inexpensive taxi or local bus, and the shops were still open. I highly recommend it.

More things about Napflio, mentioned above: it was actually the capital of modern Greece before Athens. It also has an outstanding outdoor market.

Another relatively nearby sight to explore from Napflio is Nemea. It has a stadium without the crowds that go to the ancient stadium ruins at Olympia, along with a fine small museum and the remains of a temple and other buildings. The stadium has a unique entryway tunnel, and we were the only visitors there on a Saturday in April, three years ago. In October you might also have the place to yourselves.

My husband and I travelled to Greece in 2019. Of the three islands we visited, Naxos, Milos and Santorini, the only one we wished we had spend LESS time on was Santorini. In our opinion, the island is well worth a short visit for the caldera view and the hike from Fira to Oia but it is mobbed with tourists, the food was mediocre compared to the rest of Greece and it's expensive. Splurge on a caldera view room to enjoy the sunset from your private patio, 2 nights and a full day to sightsee is plenty. BTW, every sunset we saw in Greece was magnificent, regardless of the location.

Are the days on Santorini to be deducted from the 10 days, or is it a whole separate 10 days?
If you were interested in an island, many pair Santorini with Naxos.
Whether it's five or 10 days, you'd be hard pressed to beat the Peloponnese for sheer number of attractions. You could easily fill 4-5 days in Nafplio and environs. If it's 10, pick a second spot in the Peloponnese. I chose Kardamyli and Dmitsana because we like hiking, but there are things to see in both of those areas as well.
Another option would be to head north. Before the pandemic, I was scheduled to explore Pelion, Meteora, and area around Thessaloniki. Delphi and Meteora would work well in your time frame, perhaps include Pelion if it's ten days.
What month will the trip occur?

As suggested up thread, we paired Santorini and Naxos after the RS Greece Tour (Sept. 2017). We would agree 3 days in Santorini is plenty. We liked Santorini for the views, cuisine and guided bus tour of the islands highlights. That said, (IMO) it didn't feel like the "Greece Experience" we wanted. Naxos on the other hand met our expectations. It gets fewer tourists, it feels quieter, more authentic & less crowded. We spent 6 nights on St. George Beach. It was a short walk to town. We had several favorite restaurants. (I would be happy to share if interested). In addition we took public transportation to visit other beaches, and the beautiful charming village of Apeiranthos. It has stunning views, wonderful cuisine and beautiful marble architecture throughout. We spent about 3 hours, had lunch and the bus returned to take us back to town. We would definitely return to this memorable island.

Edited to add: One of my favorite blogs highlights Greece/Naxos. www.earthtrekkers.com

I wouldn’t spend more one or to nights on Santorini. There are so many better places in Greece that actually feel Greek to spend your time.

I visited Peloponnese with my wife and 2 kids in September 2020 and we enjoyed Nauplion and Olympia. The castle and the old town of Nauplion were beautiful and we used it as our base to visit Epidaurus.

In Olympia we had the highlight of our trip to Greece. We rented virtual reality glasses and we could see every monument as it was thousands of years ago. It was amazing.

An audioguide is also integrated to the device with interesting stories for everything you look at.
This should be available in every Archaeological Site but for now it is available only in Olympia.
Here is the website we booked them from www.olympiabackintime.com

Thank you fro the great suggestions. To answer a previous question, the entire trip will be 10 12 days.

I would recommend Nafplio, as it is a great base to tour other places (historical sites, wineries etc.) as well as a beautiful place in and of itself. We had a terrific stay at Aetoma Hotel; Pan and Akis embody Greek hospitality! We spent 3 nights in a cave home (Lithies) on the caldera in Santorini and it was just the right amount of time for us. Naxos is an entirely different island that we also enjoyed immensely. It's an easy ferry ride from Santorini. If you do go to Naxos, I would highly recommend that you consider booking a private tour with Nicolas at Naxos Discovery. https://www.naxosdiscovery.net/ Truly one of the highlights of our time in Greece. Enjoy your trip!

Hi there,
while you ve been already in Crete and you definitely want to spend 4-5 days in Santorini, the best for you is to stay in the region of Cyclades in order to spend as less time on boat transportations or less money on flight tickets (they are very expensive till the end of October). I d propose you 2 or 3 little Cycladian islands close to Santorini. Folegandros, Ios or Anafi. In contrast of Santorini they are less crowdy and you will enjoy some relaxing holidays!

Another vote for only 2 nights on Santorini. Naxos and/or Paros time instead. Both easy ferry ride from Santorini. Naxos easy flight to Athens. Nafplio & area not to be missed. Car rental at Athens airport and drive to Nafplio and back. Bus from Nafplio to other sites takes too much time. Too much to see and do - not enough time on this trip. DO spend some down time on Naxos/Paros/Nafplio and people watch.

great suggestions

Santorini no.
Hydra YES.