The park's terrain varies from the short and long grass, open plains in the south, the acacia savanna in the central area, the hilly, more densely wooded northern section, and the extensive woodland and black clay plains, dominated by the central ranges of mountains in the western corridor. The plains are dotted with rocky outcrops known as "kopjes", and there are several rivers running through the park, notably the Seronera river in the central area, the Grumeti river in the Western corridor and the Mara river in the north.
Over a million wildebeest and about 200,000 zebras flow south from the northern hills to the southern plains for the short rains every October and November, and then swirl west and north after the long rains in April, May and June. So strong is the ancient instinct to move that no drought, gorge or crocodile infested river can hold them back. This annual migration through the Serengeti and the Masai Mara attract visitors from around the world, who flock to the open plains to witness the largest mass movement of land mammals on the planet.
