Santorini is an island.
Santorini . It is the largest island of a small , circular archipelago which bears the same name and is the remnant of a volcanic caldera . It forms the southernmost member of the Cyclades group of islands , with an area of approximately 73 km2 and a 2011 census population of 15,550 . The municipality of Santorini includes the inhabited islands of Santorini and Therasia and the uninhabited islands of Nea Kameni , Palaia Kameni , Aspronisi , and Christiana . The main island slopes downward to the Aegean Sea . The island is the site of one of the largest volcanic eruptions in recorded history : the Minoan eruption ( sometimes called the Thera eruption ) , which occurred some 3,600 years ago at the height of the Minoan civilization .