The Ngorongoro 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)
The area contains over 25,000 large animals including 26 black rhinoceros. There are 7,000 wildebeests, 4,000 zebras, 3,000 eland and 3,000 Grant’s and Thomson’s gazelles. The crater also has the densest known population of lions, numbering 62. Higher up, in the rainforests of the crater rim, are leopards, about 30 large elephants, mountain reedbuck and more than 4,000 buffalos, spotted hyenas, jackals, rare wild dogs, cheetahs, and other felines.
The legendary annual wildebeest and zebra migration also passes through Ngorongoro, when the 1.7 million ungulates move south into the area in December then move out heading north in June. The migrants passing through the plains of the reserve include 1.7 million wildebeest, 260,000 zebra, and 470,000 gazelles. The Lake Ndutu area to the west has significant cheetah and lion populations. Over 500 species of bird have been recorded within the NCA. These include ostrich, white pelican, and greater and lesser flamingo on Lake Magadi within the crater, Lake Ndutu, and in the Empakaai Crater Lake, where a vast bird population can be observed.
Ngorongoro is home to lush green, rain-watered vegetation, as well as desert plants. The area has uncultivated lowland vegetation, arid and semi-arid plant communities, abundant short grass used for grazing, and highland forests.
Scrub heath, grasslands, high open moorland, and the remains of dense evergreen forests cover the steep slopes of the crater, while highland trees including Peacock Flower, Yellow-Wood, Kousso (Hagenia abyssinica), and Sweet Olive can also be found. There are also extensive stretches of pure bamboo on Oldeani Mountain, and Pencil Cedar on Makarut Mountain to the west. Dove- weeds dominate the lower slopes, while the upland woodlands contain Red Thorn Acacia and Gum Acacia that are critical for protecting the watershed.
The crater basin is covered by open short grass plains with fresh and brackish water lakes, marshes, swamps, and two patches of Acacia woodland. The Lerai Forest is home to the Yellow Fever tree and Acacia, while Laiyanai Forest has Pillar Wood and Acacia Lahai. The undulating plains to the west are grass-covered with occasional Umbrella Acacia and Commiphora Africana trees. Blackthorn Acacia and Zebrawood dominate in the drier conditions beside Lake Eyasi. These extensive grasslands and bush are rich, relatively untouched by cultivation, and support very large animal populations.