Olduvai Gorge is the Archaeological Site in the north-east of Tanzania within Ngorongoro Conservation Area, in which early human fossils were first discovered in 1911 by German entomologist who was looking for butterflies The name was derived from early European miss-spelling of “Oldupai” the Maasai name for the plants that grow in that area. It has amazing landscape that resulted from the tectonic forces which created the Great Rift Valley million of years ago. Long ago the area was covered by ancient salt lake which vanished and leaving  salt deposits exposed in its walls until today.    The steep sided gorges is nearly 90 meters high and its extension  is 50 kilometers long. The importance of this area lies on the uncovered archeological remains; fossils remains, including the bones of early hominids, stone tools, marks and a building site. Other sites within the area are Laetoli site, Lake Ndutu Sites, and Nasera Rock Shelter. Apart from Olduvai Gorge, which reminds us of the origin of mankind, there are also the ruins of the ancient city, which are marked by stone terrace and the complex irrigation system at Engaruka within Conservation Area Shifting Sands: There is the volcanic ash dune of Shifting Sands situated near Olduvai Gorge. These crescent-shaped mounds are a remarkable phenomenon. Technically they are known as barkan, and they result if there is sufficient dust on the ground and a unidirectional wind to blow it. The dust collects around a stone, and this collection accumulates more. The process continues, with the mound growing all the time, and then it begins to move. The crescents have their two sharp arms pointing the way the wind is going, and the whole shape is beautifully symmetrical.