Atlantis is not hiding at the bottom of the Atlantic Ocean but in plain view on top of the Sahara Desert. The prosperity of the Atlas Empire and the inundation of Atlantis corresponded to a lush Green Sahara started around 12,000 years ago. About 5700 years ago, the Green Sahara suddenly began to wither from the Atlas Basin, the heartland of the Atlas Empire. This is the rain shadow area of the Atlas Mountain range in today’s Northeast Algeria and South Tunisia. When the water cycle stability in this standalone catchment was broken, the Chotts Megalakes (the Atlantic Sea) dried rapidly and the strong rain shadow effect of the Atlas Mountain became fully active. Deserts formed immediately in this area and gradually expanded east and south, like a spreading wildfire powered by the prevailing winds. This led to desertification and aridification in North Africa, West Asia, and the Mediterranean synchronously until this day. This timeline spans most of human history as we know it, including the thriving and dispersion of Atlas Empire, the rise and fall of Egypt, the prosperity and desolation of Mesopotamia, and the civilization shifts first from west to east and then from east to west across the Mediterranean and the Atlantic. The Atlantic Sea had a surface area over 26,000 sq km, which generated a great amount of water vapor, sufficient to eliminate the strong rain shadow effect of the Atlas Mountain, so that the Green Sahara was stabilized for about six thousand years. The Earth’s precession (wobbling) has been blamed as the main control for the flipping between desert and green in the Sahara. This view has misled the academic society away from seeking the true primary cause for so long. The water cycle stability of the Sahara is governed by the non-linear relationship between precipitation and evaporation, which depends on surface conditions and atmospheric circulation. The Earth’s precession only moved the water cycle closer to its unstable point so that a perturbation could trigger the transition from wet to dry state. This book explains the start and step-by-step spread of the Sahara Desert and its impact on West Asia and the Mediterranean regions. Archaeological records and paleoclimate data corroborate this new insight of the Sahara expansion process and the consequential desertification in these areas. The desertification process in Northwest China is an independent validation for the same control mechanism. Based on the new understanding, approaches are suggested to revive the Northwest China ecosystem, to turn the Sahara back to green and to ameliorate Australia to a water abundant country.