Rhodes and Kos both have their own airports with seasonal direct flights, which is usually the sane way in. Ferries run down from Athens, but they are long. So this is not a route you sail down from Piraeus - it is a group you fly into and then hop around inside.
That is good news for a shorter trip: you land in the middle of the group rather than spending a day getting to it.
The two anchors
Rhodes is a walled medieval city with a large island behind it, and it has an unusually long season - longer than the Aegean norm, which matters at either shoulder.
Kos is flat and cyclable, with the Asklepion and a Roman town.
Either works as the base, and the honest split is: Rhodes if you want the Old Town and more to see, Kos for flat easy beach days. Kos vs Rhodes settles it properly.
The small islands are the reason to come
This is where the group earns the trip. Within short hops of the two anchors:
- Symi - one neoclassical harbour, stacked in colour.
- Nisyros - an active volcano you can walk down into.
- Patmos - the cave of the Apocalypse and a fortified monastery.
- Kalymnos - sponge divers, and now world-class sport climbing.
- Karpathos - wind, remote villages and a long empty west coast.
- Astypalaia - two lobes, one isthmus, and a Cycladic-looking chora.
- Kasos - the southernmost, with a story rather than sights.
A shape that works
Ten days, two anchors. Fly into Rhodes, give it three or four nights including the Old Town, take Symi as a night rather than a day trip, then move up to Kos for the second half with Nisyros as the boat day and Kalymnos as the other.
That route uses both airports, which means flying out of the one you did not fly into and never doubling back. Rhodes to Kos is the main Dodecanese link and the leg that joins the two halves.
A week does one anchor and two small islands. Patmos sits further north and suits a trip that is about the monastery rather than the beaches - Athens to Patmos calls it the long way to a quiet island, which tells you where it belongs.
Symi as a night, not a day
Worth stating separately. Symi fills with day-trip groups off the Rhodes boats around the middle of the day, and in the late afternoon the excursion boats cast off and the island settles back to its own pace.
A swim or a dinner after that shift is a different experience from one before it - which is the case for staying the night, in one sentence. Our Symi guide has the rest.
Where this route breaks
Trying to reach it from the Cyclades. Different group, different lines. Mixing costs days.
Assuming the small islands run like the big ones. Sailings between them are thinner and more seasonal than the Rhodes-Kos link, so build the route with the small hops first and the anchors around them, not the other way round.
The Dodecanese has each island, and the island-hopping guide covers sequencing.