Ngorongoro Crater is the world's largest unbroken volcanic caldera. The crater is 610m deep and the floor is 260km squared. The steep sides of the crater mean that it has become a natural enclosure for a wide variety of wildlife. Ngorongoro comes from a Masai word, llkorongoro which was the name given to the age group of Masai warriors who wrested the highlands from the datong, their previous occupants. The datong had in turn taken them from their predecessors the Hadzabe (bushmen/hunter-gatherers). The name llkorongoro echoed the sound of the battle bells the Masai warriors wore when they first occupied the highlands in the year 1800. Aside from herds of zebra, gazelle and wildebeest, the crater is home to the "big five" of black rhinoceros, lion, leopard, elephant and buffalo. The crater plays host to almost every individual species of wildlife in East Africa, and there are an estimated 25,000 animals within the crater. Lake Magadi in the centre of the crater is, like many in the rift valley, a soda lake supporting flocks of flamingo.