The present-day crescent shape of the island is a consequence of the activity of the volcano in prehistoric times feeding the myth of the lost Atlantis. Santorini is essentially what remains of an enormous volcanic explosion dated back 3,600 years and which created 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), surrounded by 300 m (980 ft) high steep cliffs on three sides.
The mild activity of the volcano after this major eruption has built up two small islands within the caldera, Palea and Nea Kameni visited by hundreds of people everyday during the tourist season.
