The Ngorongoro Conservation Area (, ) is a protected area and a UNESCO World Heritage Site located in Ngorongoro District, west of Arusha City in Arusha Region, within the Crater Highlands geological area of northern Tanzania. The area is named after Ngorongoro Crater, a large volcanic caldera within the area. The Ngorongoro Conservation Area Authority administers the conservation area, an arm of the Tanzanian government, and its boundaries follow the boundary of the Ngorongoro District in Arusha Region. The western portion of the park abuts the Serengeti National Park (also a UNESCO World Heritage Site), and the area comprising the two parks and Kenya's Maasai Mara game reserve is home to Great Migration, a massive annual migration of millions of wildebeest, zebras, gazelles, and other animals. The conservation area also contains Olduvai Gorge, one of the most important paleoanthropological sites in the world. The 2009 Ngorongoro Wildlife Conservation Act placed new restrictions on human settlement and subsistence farming in the Crater, displacing Maasai pastoralists, most of whom had been relocated to Ngorongoro from their ancestral lands to the north when the British colonial government established Serengeti National Park in 1959. History and geography The name of the crater has an onomatopoeic origin; it was named by the Maasai pastoralists after the sound produced by the cowbell (ngoro ngoro). Based on fossil evidence found at the Olduvai Gorge, various hominid species have occupied the area for 3 million years. Hunter-gatherers were replaced by pastoralists a few thousand years ago. The Mbulu came to the area about 2,000 years ago and were joined by the Datooga around the year 1700. Both groups were driven from the area by the Maasai in the 1800s. No Europeans are known to have set foot in the Ngorongoro Crater until 1892 when it was visited by Oscar Baumann. Two German brothers (Adolph and Friedrich Siedentopf) farmed in the crater until the outbreak of World War I, after leasing the land from the administration of German East Africa. The brothers regularly organized shooting parties to entertain their German friends. They also attempted to drive the wildebeest herds out of the crater. In 1921, the first game preservation ordinance was passed, which restricted hunting to permit holders throughout Tanzania. In 1928, hunting was prohibited on all land within the crater rim, except the former Siedentopf farms. The National Park Ordinance of 1948 (implemented in 1951) created the Serengeti