Some 9,000 years earlier, according to the legend, there was an island metropolis, roughly 32,000 square miles in area, lying beyond the Pillars of Hercules (the modern-day Straits of Gibraltar). It was dominated by hills and surrounded by two concentric rings of land, linked by bridges and roads. The water separating the rings formed extensive harbors connected by canals 150 feet deep and 500 yards wide. The vegetation was luxuriant, the land fertile and self-sufficient, and there were both hot and cold freshwater springs. Black, white, and red stones were quarried from beneath the central hill, leaving a natural roof for the inner harbor. The Atlanteans lived securely and comfortably in their island paradise – until, suddenly, disaster struck. According to Plato : "Through violent earthquakes and floods, in a single day and night of misfortune [the whole race] was swallowed up by the Earth and the island of Atlantis disappeared into the depths of the sea.