Amorgos, Anafi, Andros, Antiparos, Delos, Ios, Kea, Kimolos, Kythnos, Milos, Mykanos, Naxos, Paros, Folegandros, Santorini, Serifos, Sifnos, Sikinos, Siros, Tinos, and many other much smaller isles which make up a group counted at 220 altogether.
Only the islands of Milos and Santorini are volcanic in origin, the other islands are considered submerged mountains. (There are nine volcanos all together in Greece and the Greek Islands.)
Map of Cyclades Islands
Related: Islands of Greece
The Acropolis in Athens Greece
The Acropolis - Parthenon and More
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Fodor's Essential Greece: with the Best Islands (Full-color Travel Guide)