This is the ideal itinerary if you want to see the largest herd movement of animals on the planet and go to the best national parks in Tanzania's north. This trip will concentrate on the western Serengeti. The great migration occurs from May to July across the Grumeti River. Before coming face to face with predators waiting on the other side, the herds of wildebeests and zebras have to outwit the enormous Nile crocodiles and the swiftly moving water. A magnificent show.