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. Ngorongoro Crater, a large volcanic caldera within the area, is recognized by one private organization as one of the seven natural wonders of Africa. 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.

Ngorongoro Crater
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 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 trees. The crater floor is mostly open grassland with two small wooded areas dominated by Acacia xanthophloea.

The Munge Stream drains Olmoti Crater to the north, and is the main water source draining into the seasonal salt lake in the center of the crater. This lake is known by two names: Makat as the Maasai called it, meaning salt; and Magadi. The Lerai Stream drains the humid forests to the south of the Crater, and it feeds the Lerai Forest on the crater floor – when there is enough rain, the Lerai drains into Lake Magadi as well. Extraction of water by lodges and NCA headquarters reduces the amount of water entering Lerai by around 25 percent.

The other major water source in the crater is the Ngoitokitok Spring, near the eastern crater wall. There is a picnic site here open to tourists and a huge swamp fed by the spring, and the area is inhabited by hippopotamus, elephants, lions, and many others. Many other small springs can be found around the crater’s floor, and these are important water supplies for the animals and local Masaai, especially during times of drought.

Approximately 25,000 large animals, mostly ungulates, live in the crater. Large animals in the crater include the black rhinoceros, the local population of which declined from about 108 in 1964-66 to between 11-14 in 1995, and the hippopotamus. There also are many other ungulates: the wildebeest (7,000), Burchell’s zebra (4,000), the common eland, and Grant’s and Thomson’s gazelles (3,000). Waterbuck occur mainly near Lerai Forest. There are no topis, oribis, or crocodiles. Impala are absent because the open woodland they prefer does not exist. Giraffe also are absent, possibly because of a lack of browse species. Cheetah, African wild dog, and leopard are rarely seen.

Although thought of as “a natural enclosure” for a very wide variety of wildlife, 20 percent or more of the wildebeest and half the zebra populations vacate the crater in the wet season. Buffalo and eland do the opposite. Their highest numbers are during the rains. The crater has one of the densest known population of lions, numbering 62.

Olduvai Gorge
The Ngorongoro Conservation Area also protects Olduvai Gorge, situated in the plains area. It is considered to be the seat of humanity after the discovery of the earliest known specimens of the human genus, Homo habilis as well as early hominidae, such as Paranthropus boisei.

The Olduvai Gorge or Oldupai Gorge is a steep-sided ravine in the Great Rift Valley, which stretches along eastern Africa. Olduvai is in the eastern Serengeti Plains in northern Tanzania and is about 30 miles long. It lies in the rain shadow of the Ngorongoro highlands and is the driest part of the region. The gorge is named after ‘Oldupaai’, the Maasai word for the wild sisal plant, Sansevieria ehrenbergii.

It is one of the most important prehistoric sites in the world and research there has been instrumental in furthering understanding of early human evolution. Excavation work there was pioneered by Mary and Louis Leakey in the 1950s and is continued today by their family. Some believe that millions of years ago, the site was that of a large lake, the shores of which were covered with successive deposits of volcanic ash. Around 500,000 years ago seismic activity diverted a nearby stream which began to cut down into the sediments, revealing seven main layers in the walls of the gorge.