The Wildebeest Migration-Kenya

Around October, nearly two million herbivores travel from the northern hills toward the southern plains, crossing the Mara River, in pursuit of the rains. In April, they then return to the north through the west, once again crossing the Mara River. This phenomenon is sometimes called the Circular Migration.
Some 250,000 wildebeest die during the journey from Tanzania to Masai Mara Reserve in lower Kenya, a total of 800 kilometres (500 mi). Death is usually from thirst, hunger, exhaustion, or predation. The migration is chronicled in the 1994 documentary film, Africa: The Serengeti.
What makes it a world class event is how the wildebeest struggle to survive with only the strongest and luckiest making it to "canaan" This event entered the Wonders of the World book in 2006.