Santorini (Greek: Σαντορίνη, pronounced [ˌsa(n)do̞ˈrini]) is a small, circular archipelago of volcanic islands located in the southern Aegean Sea, about 200 km (120 mi) southeast from Greece's mainland. It is also known as Thēra (or Thira, Greek Θήρα [ˈθira]), forming the southernmost member of the Cyclades group of islands, with an area of approximately 73 km2 (28 sq mi) and a 2001 census population of 13,670. It is composed of the Municipality of Thira (pop. 12,440) and the Community of Oía (Οία, pop. 1,230, which includes 268 inhabitants resident on the offshore island of Therasia, lying to the west). These have a total land area of 90.623 km2 (34.990 sq mi), which also includes the uninhabited islands of Nea Kameni, Palaia Kameni, Aspronisi, and Christiana (all part of the Municipality of Thira).
Santorini is essentially what remains of an enormous volcanic explosion, destroying the earliest settlements on what was formerly a single island, and leading to the creation of the current geological caldera.