This is a natural wonder in its own right; the Ngorongoro Crater is an ancient volcanic caldera that harbors an incredible density of wildlife. Located in northern Tanzania, the crater floor is home to the Big Five, including one of the highest concentrations of lions in Africa.
But the crater is probably best known as a haven for the rare black rhino. Apparently each of these impressive creatures is guarded by two (armed) park rangers constantly.
Accessing the park involves driving down to the crater floor. That in itself is an experience. The dramatic scenery, with towering crater walls enclosing vast grasslands and lakes, makes for some of the most spectacular safari photography.