6 nights in greece but where? No car and no rowdy crowds

Indeed, Milos and Tinos are two islands that require your own means of transportation.

By not renting a car, you seriously limit your options and will most of the time be forced to stay in the main town, which in July will be very touristy and bustling.

So your preferences are somewhat incompatible.

However, one island that might suit you is Sifnos.
Very typically "Cycladic," more unspoiled than Naxos, Paros, or Milos, with a charming capital, Apollonia, located in the center. It is also the hub of an excellent network of six bus lines that operate until late in the summer and connect all the seaside villages on the south coast.
Of course, this advantage comes at a price: you have to get there by ferry. There is no airport. Ferry travel times from Piraeus vary depending on the ferry type, from 2.5 hours to... over 6 hours.

I've stayed in quite a few places on Sifnos over the years, and I can't think of one that wouldn't suit you, except perhaps Kamares, the ferry port, which I wouldn't recommend.
My last stay on Sifnos was in the former capital, Kastro, here (but it's not a hotel). The streets and alleys in the village are not accessible by car, only on foot or by donkey. So, peace and quiet are guaranteed! And breathtaking views, even better than Santorini.

https://www.arismaria-traditional.com/en/

Sifnos website:

https://sifnos.e-sifnos.com/index.php

Another locally managed website with a list of accommodations:

https://www.roomsinsifnos.com/

I’d definitely recommend Sifnos too, having been there in 2023, and, also though we had a car, from what we saw and spoke to other tourists, the bus system gets one everywhere. The food is divine, the beaches even better. We stayed in Faros, which is slightly off the beaten path yet still has two luxury hotels, albeit small ones. We spent 9 days on Sifnos and wished it could’ve been more. Very welcoming, friendly people. Then again, isn’t all of Greece that way? Good luck and happy travels.

Thank you both for your v helpful replies - Sifnos sounds wonderful, and perfect for where we want to be/go, my only concern is getting there and back from the airport - that bit sounds like a bit of a nightmare and not very straightforward at all?

You don't have any other options about getting from the airport to an island if there is no airport at the island which you can go directly to once you land in Athens.

However, that depends on scheduling of the flight.

Your other option is to take the metro or bus from the airport to the port of Piraeus then a ferry to an island.

The closest islands to the mainland are the Saronic Islands and the two best would be Aegina or Poros which are both relatively small but offer just about what most people go to a Greek Island for.

If you want something geared for beaches and family activities then Agistri is a good option. Good for walking or even riding a bike as distances are not that far.

Another option is Hydra where there is no other transportation other than your feet as vehicles are not allowed on the island.

July will be high season so most islands will have tourists.

https://unfoldinggreece.com/saronic-islands-greece/

If you want to go directly to an island that has an airport direct from Athens then you can check out this list of island airports and figure out which one suits you.

However, scheduling could be a problem upon arrival in Athens to an island airport.

https://offbeatgreece.com/greek-islands-airports/

I've seen your previous posts about Greece, and it turns out you have a fair amount of apprehension, but getting from the airport to the port and back is absolutely no nightmare. Thousands of travelers, many of them first-timers, do this every week.
You just need a flight landing early enough to catch a ferry.

If you land around noon or before, you can take the Superrunner Jet II ferry, which departs at 3:20 PM.

From the airport, there are 3 ways to get to the port of Piraeus:

1 - A taxi that will drop you off 50 minutes later at the dock in front of the ferry (around €60)

2 - The metro, which is direct to the port of Piraeus, where you'll arrive 60 minutes later (€9)

3 - The X96 bus, which will drop you off at the port about an hour later depending on traffic (€5.50)

Anyone will confirm that there's nothing challenging about it.

If you allow 2.5 hours (or 3 hours for a safe margin) between landing time and ferry departure time, you're fine.

See the ferry schedules to Sifnos from the beginning of July: (change the date if necessary):

http://www.openseas.gr/PIR/SIF/2025-07-03/2025-07-03/itineraries

Shelly please thank Jo-Lui for her wonderful gift of key information! She makes the options crystal-clear for getting to Sifnos without stress. Parenthetically, I often find that UK people are apprehensive when they cannot find a plane that goes directly from their nearby airport immediately to their chosen isle. It's important to realize that this mainly is offered when there is massive touristm traffic to purpose-built "resort areas" ... which defeats your wish to experience "authentic side of Greece." Sifnos so far has escaped the invading armies because of that one extra step required (hurray!). Thank your lucky stars and hurry there before things change.

Another vote for Sifnos! Also concur that getting from the airport, or the city for that matter, to Piraeus is easily done. Worry not!

I don’t think Brits are apprehensive about travel - it’s more that we value our holiday too much to want to waste excess time travelling and a lot of people simply want sun, sea and relaxation rather than adventure. With flights and a ferry it’s going to take a minimum of 13-14 hours door to door to get to somewhere like Sifnos. That’s probably double the travel time to Crete.

Thank you everyone for all your extremely informative and helpful replies. However I do think that Helen has probably put my niggling doubts about getting to some of the lovelier and quieter Greek islands into words in a nutshell with her comments; the idea of having to travel 13-14 hours each way to get to a 'holiday' destination, adding in the stress factors of delayed ferries and trying to make flight connections depending on local transport does not really gel with my idea of a relaxing start to a vacation. It's a fairly long flight to Greece (and maybe up at dawn for an early morning flight or middle of the night flight from London) to have to then get a bus to a ferry port and then wait for a ferry and spend another 3-5 hours getting to the island doesn't really appeal to me. I know, I know, it's worth it to escape the crowds of mainland Greece, but if you only have 6 days it doesn't really justify the length of time getting there and then doing the same getting back again. Maybe if I was a young backpacker on a gap year or had a longer vacation time I might consider it.......

Last year we stayed in Rhodes Old Town. Our accommodation was away from the maddening crowds. So at the end of our day, we walked to the upper end of the walled city to our apartment. No crowds once we left the touristed streets. This was in May. Probably many more tourists in summer, however it's the cruise ships that bring in the most day travellers. Our accommodation was Georges Old Town Apartment, but there were other classier hotels nearby.

Most of the night life in the Old Town is closer to the seaside of the town. If you want to go to a beach you'll need to walk to the New Town.