Santorini is a group of five volcanic islands in the Aegean Sea. Thira (also called Santorini) is the main island and around it Thirasia and Aspronisi and the two volcanic islands Palea Kameni and Nea Kameni. It was one island named Stroggili (circle in Greek) until about 1645 BC, when the volcano in the middle of the island erupted and Caldera was created. Someone says that Santorini is that mythical Atlantis gone under the sea. The two black islands appeared much later from various eruptions. The last one was in 1950.