Santorini is really five islands: Thira, Thirasia, Palea Kameni, Nea Kameni and the Aspronisi. It is the most southeast island of the Cyclades. Before 1645 BC this was one island, called Stroggili, with an active volcano in the middle. Santorini covers 132 square Kilometers and is located 127 nautical miles from the port of Piraeus to the SSE.
About 1500 BC, the volcano, photo below, erupted, a huge crater was created; then the sea rushed in to fill the crater and the three modern islands remained. (Experts estimate that a tidal wave about 100 m high resulted from this eruption; this tidal wave did major damage to the north coast of Crete.) The sea filled crater is called a caldera. According to the vote of "Travel & Leisure" magazine Santorini is the most popular vacation destination in Europe and the island has the 7th position among the 10 most popular world-wide islands. The volcano surrounded by the blue waters of the Aegean sea is the most breath-taking one on this planet.