Santorini (, pronounced ), classically Thera (English pronunciation ), and officially Thira (Greek: Θήρα ), is an island in the southern Aegean Sea, about southeast of Greece's mainland. 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 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 total land area is . Santorini is part of the Thira regional unit.