The Ngorongoro Conservation Area (NCA) is a conservation area and a UNESCO World Heritage Site located 180 km (110 mi) west of Arusha in the Crater Highlands area of Tanzania. The area is named after Ngorongoro Crater, a large volcanic caldera within the area. The conservation area is administered by the Ngorongoro Conservation Area Authority, an arm of the Tanzanian government, and its boundaries follow the boundary of the Ngorongoro Division of the Arusha Region.
It has been reported in 2009 that the government authority has proposed a reduction of the population of the conservation area from 65,000 to 25,000. There are plans being considered for 14 more luxury tourist hotels, so people can access "the unparalleled beauty of one of the world's most unchanged wildlife sanctuaries".
The main feature of the Ngorongoro Conservation Authority is the Ngorongoro Crater, the world's largest inactive, intact, and unfilled volcanic caldera. The crater, which formed when a large volcano exploded and collapsed on itself two to three million years ago, is 610 metres (2,000 feet) deep and its floor covers 260 square kilometres (100 square miles).
Estimates of the height of the original volcano range from 4,500 to 5,800 metres (14,800 to 19,000 feet) high. The elevation of the crater floor is 1,800 metres (5,900 feet) above sea level. The Crater was voted by Seven Natural Wonders as one of the Seven Natural Wonders of Africa in Arusha, Tanzania in February 2013.
The crater highlands on the side facing the easterly trade winds receives 800 to 1,200 millimetres (31 to 47 inches) of rain a year and are covered largely in montane forest. The less-steep west wall receives only 400 to 600 millimetres (16 to 24 inches) and is grassland and bushland dotted with Euphorbia bussei (es) trees. The crater floor is mostly open grassland with two small wooded areas dominated by Acacia xanthophloea.