Everyone is overwhelmed by their first sight of the Ngorongoro Crater, in northern Tanzania. The immense scale, the grandeur, the aesthetic perfection of the landscape, all prompt wonder and incredulity. You stare and stare at the dark-green walls of the caldera, cradling a sky-blue soda lake, home to tens of thousands of pink flamingos. And although you can’t see them from high on the rim, you are aware that down on the crater floor, 2,000 feet below, lives a Noah’s Ark of animals, including around 60 lions.