Get to know Santorini island The panoramic volcanic island is a member of the Cycladic Island in the southeastern part of Greece, 200km away from the mainland. It is the largest island in a small region known as Archipelago, found at the south of the Aegean Sea. With Phira as its capital (it is also referred to as Thira), Santorini is a volcanic remain after a volcanic eruption dated back 3500 years ago. It is also among the most vibrant islands in Greece.