First of all, I will like to propose the official site of the Greek ministry of culture, where you can find in details accurate information on the historical - archeological places of Greece: http://www.culture.gr and especially http://www.culture.gr/2/21/toc/index.html

I have search the Internet and I have found some interesting sites, which I propose to visit before deciding for your trip:

About Peloponnissos http://www.greecetravel.com/peleponisos/index.html http://dilos.com/region/pelopon/index.html

About Monemvassia http://users.otenet.gr/~panosmon/monemvasia.htm

About Geraki (a place close to Monemvassia) http://users.hol.gr/~geraki/

And a correction: Yesterday I have written for the temple of Apollon in Vrysses. The correct is temple of Apollon in Vasses (have a look at the site http://www.culture.gr/2/21/211/21107n/e211gn02.html).

From the islands you have chosen, Santorini is the most famous and most interesting. It's not only the natural beauty what makes the island attractive, but also its past: In Acrotiri there are the ruins of one of the most important prehistoric settlements of the ancient world, where the first habitation dates from the Late Neolithic times (at least the 4th millennium B.C.)!!!!. In the town of Ancient Thera, the Classical city of the island (which was founded in the 9th century B.C. by Dorian colonists and continued to be inhabited until the early Byzantine period) where the ruins belong to the Hellenistic and Roman phases of the town. And the volcano, the medieval town etc....

For details have a look at http://www.culture.gr/2/21/211/21121a/e211ua08.html (Akrotiri) or http://dilos.com/region/cyclad/akrotiri.html http://www.culture.gr/2/21/211/21121a/e211ua05.html (Ancient Thira)

There are some sites with general information on Santorini http://www.santorini.com/ http://www.areianet.gr/infoxenios/english/cyclades/sandorini/sandorini.html (very accurate info)

The only problem is that for Santorini September is high season and you maybe can not easily find a room with view to volcano without paying a fortune. It's also overcrowded, especially with German tourists. Last year I wanted to go there with my Italian friends but the cost was prohibitive, so we have been to Sifnos instead of Santorini. And of course you need more that 4 days to round the island.

Milos has the best beaches, nice villages and you can see the place where the famous statue of Venus of Milos (now in Louvre museum, in Paris) was found and stolen, and the catacombs from the early Christian period.

At the site: http://www.areianet.gr/infoxenios/english/cyclades/milos/milos.html you can find a lot of info on the island. You need 3 or more days to see all the island. You must not miss a tour (by boat) around the island with stop to the famous cave Kleftiko.

Serifos is a small nice island, but I don't suggest it as the first choice. I propose you Sifnos or my most favorite Paros instead. Have a look at the site http://www.areianet.gr/infoxenios/english/cyclades/sifnos/sifnos.html (Sifnos) and http://www.areianet.gr/infoxenios/english/cyclades/paros/paros.html or http://cyclades.forthnet.gr/paros/index.htm (Paros).

Both need 4 days for a complete tour.

And some general information: all the islands have connection by boat with the port of Pireas (Athens), but it's not sure that there is a direct connection between them (without having to come back in Pireas). So you have to choose to visit islands with direct connection.

In the site http://www.gtpnet.com/topeng.htm you can find the sea schedules of the ferries or hydrofoils that connect the islands.

Please don't hesitate to ask me for more.

Ciao Joanna in Athens