It is the largest island of a small, circular archipelago which bears the same name. It forms 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. The municipality of Santorini is composed of the islands of Santorini, Therasia, and the uninhabited islands of Nea Kameni, Palaia Kameni, Aspronisi, and Christiana.
Santorini is essentially what remains of an enormous volcanic explosion that destroyed the earliest settlements on what was formerly a single island, which led to the creation of the current geological caldera.
A giant central lagoon, more or less rectangular, and measuring about 12 by 7 km (7.5 by 4.3 mi), is surrounded by 300 m (980 ft) high steep cliffs on three sides. The island slopes downward from the cliffs to the surrounding Aegean Sea.
On the fourth side, the lagoon is separated from the sea by another much smaller island called Therasia; the lagoon merges with the sea in two places, in the northwest and southwest. The water in the centre of the lagoon is nearly 400 m (1,300 ft) deep, thus making it a safe harbour for all kinds of shipping. The island’s harbours all lie in the lagoon and there are no ports on the outer perimeter of the island; the capital, Fira, clings to the top of the cliff looking down on the lagoon. The volcanic rocks present from the prior eruptions feature olivine and have a notably small presence of hornblende.
Excavations starting in 1967 at the site called Akrotiri under the late Professor Spyridon Marinatos have made Thera the best-known “Minoan” site outside of Crete, the homeland of the culture. The island was not known as Thera at this time. Only the southern tip of a large town has been uncovered, yet it has revealed complexes of multi-level buildings, streets, and squares with remains of walls standing as high as eight metres, all entombed in the solidified ash of the famous eruption of Thera.
The site was not a palace-complex such as are found in Crete, but its excellent masonry and fine wall-paintings show that this was certainly no conglomeration of merchants’ warehousing either. A loom-workshop suggests organized textile weaving for export. This Bronze Age civilization thrived between 3000 to 2000 BC, and reached its peak in the period 2000 to 1580 BC.