Ngorongoro Conservation Area
Considered to be "the cradle of civilization".
Flora and fauna
Fauna: Lions are in the highest density in the world in the crater, so there is a good chance of seeing them. There are herds of wildebeest, zebra, and a lot of buffalo and Grants' gazelles too. This is one of the best places in East Africa to see a Black Rhino. Hippos and flamingos are seen in Lake Magadi. Hyenas are a common predator, and cheetahs are frequently seen. Leopards are in the conservation area but rarely seen, along with wild dogs.
It's a good idea to contact the Ngorongoro Crater Conservation Area Authority to help plan in advance. Most people come to Ngorongoro from Arusha on organized safaris. It is, however, cheaper to organize a safari from Karatu, a town 10km from the gates. Here you can organize a safari with an independent driver. If using an independent driver, the profit will go to an individual Tanzanian instead of a larger safari company, however these vehicles are less reliable and are known to have parts fall off while driving around the crater. That can add or detract from your experience, depending on what you're looking for.
For foreigners : $50 per person/day. $200 per car/day. (not a car full of people, just the car.)
For Tanzanians it's 15,000/= per day. Park fees are necessary for the operation of the parks.