The Santorini Islands are a small group of volcanic islands located in the Aegean Sea, approximately 200km southeast from the mainland of Greece. It is also known as Thira or Thera, the name of the largest island. It is the most south of the Cyclades group of islands, with an area of about 73 sq km, and an estimated population of approximately 15,000 people. It is the home of the most active volcanic center in the Aegean Arc, including the largest volcanic eruptions of the last several thousand years when it erupted around 3,500 years ago. The eruption left a large whole surrounded by volcanic ash deposits which are hundreds of feet deep. Unfortunately for volcano watchers, the only thing left is a caldera, which is the geologic result of a volcano folding in on itself. While the caldera is interesting to investigate; there are possible dangers, so one must take the necessary precautions.