Santorini or classically Thira is essentially what remains after an enormous volcanic eruption that destroyed the earliest settlements on a formerly single island, and created the current geological Caldera. A giant central, rectangular lagoon which is surrounded by high, steep cliffs.

Santorini’s history and current landscape are defined by its status as a volcanic caldera. The island's iconic crescent shape was created by the "Minoan Eruption" around 1600 BC, one of the largest volcanic events in human history, which devastated the local civilization and possibly inspired the myth of Atlantis. More recently, in early 2025, Santorini experienced a period of significant seismic unrest. Between January and March 2025, a series of earthquakes—some reaching a magnitude of 4.9—prompted the Greek government to declare a temporary state of emergency. While scientists confirmed these tremors were tectonic rather than volcanic, they caused brief disruptions to ferry services and led to temporary restrictions in high-congestion areas like the Old Port of Fira. As of February 2026, the island is fully open and safe for tourism, though geological monitoring remains intensive. The "unrest" has served as a reminder that the volcanic island is a living geological site, though the caldera remains stable and no volcanic eruption has occurred since the minor event in 1950.