More specifically, the study shows that around 9600 BC, when according to Plato Atlantis was above water, the modern Cyclades Islands were connected by the Cyclades Plateau, a flat terrain (now 400 feet below sea level,) that formed the body of a huge island. When this prehistoric island is compared to Plato's Atlantis, it immediately becomes evident that this must have been the land Plato was talking about. Its northern region was comprised of mountains that reached the shores. Below the mountainous region there was an oblong valley measuring 555 Km 2. Below the oblong valley there was a smaller valley, 2/3 the size of the oblong valley that measured 370 Km 2. This was the primary island. Nine kilometers away from the primary island, and precisely as Plato depicted, lies the island of Santorini, a circular island with a flooded core and a small island in its center (Santorini, an island within an island setting, a sea volcano with a collapsed center, prior to the volcanic eruption of 1600 BC had a single opening on its outer ring that allowed ships to enter its watery caldera).