A view of animals and tourists inside Ngorongoro Crater in Tanzania's Ngorongoro Conservation Area, a UNESCO World Heritage Site. The crater is a large volcanic caldera, which formed when a giant volcano exploded and collapsed on itself some two to three million years ago. It is 610 m (2,000 ft) deep and its floor covers 260 km2 (100 sq mi).Photo: Muhammad Mahdi Karim