Three million years ago, Ngorongoro, one of the highest peaks in Africa, towered alongside Kilimanjaro in northern Tanzania. Our earliest ancestors witnessed the restless volcano's collapse, forming what is today the world's largest intact caldera (likened to a giant soup bowl with a flat base and steep sides.) Today, Ngorongoro remains a place of drama and beauty - the most remarkable wildlife haven on our planet.

Ngorongoro Crater, 12 miles wide, is the world's largest intact caldera. Before the cataclysmic collapse of its cone 2 million years ago, this volcanic mountain may have been taller than Kilimanjaro. Its rim, which averages 7,600 feet elevation, is cloaked in moist montane forest and grassland, hosting elephants, golden-winged and eastern double-collared sunbirds, stonechats and Jackson's widowbird. At 5,600 feet elevation, the crater floor is primarily grassland, with patches of spring-fed marshes, freshwater ponds, a salt lake, and small forests.

The Crater is an African Eden, teeming with 30,000 wild animals, including black rhino, elephant, leopard, buffalo, cheetah, hyena, zebra, wildebeest, warthog, hippo, Thomson's gazelle, eland and reedbuck as well as prides of lion that include the magnificent black-maned males. For those who wish to see the fierce cats of Tanzania, the crater is a dream come true: an abundance of predators are drawn by the vast herds of antelope. The golden jackal is frequently seen during the day, while the black-backed jackal and bat-eared fox are most active after dark. There are lots of colorful flamingoes and a variety of other water birds around the soda lake on the crater floor. More than a 100 species of bird not found in the Serengeti have been found in the crater.

In the conservation area, which covers almost 5,000 square miles, 42,000 Maasai live and farm in harmony with wild and dangerous animals. The area also has a special place in the heart of African conservationists: On the rim of the crater stands a simple memorial. It commemorates Michael Grzimek, who died here in 1959 while filming the epic African documentary, "Serengeti Shall Not Die". The inscription reads simply: "he gave all he possessed for the wild animals of Africa, including his life."

The Ngorongoro Crater is part of the equatorial Serengeti ecosystem, along with the Maasai Mara Game Reserve and Serengeti National Park. Unlike the latter two wildlife sanctuaries, migration here is modest because the Ngorongoro Crater has an abundant year-round water supply and the precipitous walls of this collapsed extinct volcano discourage (but don't totally eliminate) migrating.

Another key difference is the animals within the Ngorongoro Crater are better habituated to us wanting to see them, so it's easier to view them up close. This is one of the reasons that some seasoned travelers believe that the Ngorongoro Crater is the best wildlife preserve in East Africa.