Santorini Thera is an island in the southern Aegean Sea, about 120 mi southeast from the Greek mainland. It’s the largest island of a small, circular archipelago, which bears the same name and is the remnant of a volcanic caldera. Santorini includes the inhabited islands of Santorini and Therasia, as well as the uninhabited islands of Nea Kameni, Palaia Kameni, Aspronisi and Christiana. The total land area is 34.990 sq mi.

The island was the site of one of the largest volcanic eruptions in recorded history: the Minoan eruption (sometimes called the Thera eruption), which occurred about 3,600 years ago at the height of the Minoan civilization. The eruption left a large caldera surrounded by volcanic ash deposits hundreds of meters deep. It may have led indirectly to the collapse of the Minoan civilization on the island of Crete, 68 mi to the south, through a gigantic tsunami. The Thera eruption may be the source of the legend of Atlantis.