The Maasai Mara National Reserve is a large reserve in southwestern Kenya. It lies on the common border with Tanzania. It is adjacent to the Serengeti National Park. Thus, a large continuous territory is created, which enables the migration of animals. It is named after the Maasai, the original inhabitants of the area and the Mara River. The first smaller reserve was established in this area in 1948. The reserve acquired its current boundaries in 1984, with an area of 1510 km². The terrain of the reserve is mainly open grassland with seasonal rivers. The dominant inhabitants of the Maasai Mara are the blue wildebeest. Around July they migrate north with other herbivores from the Serengeti plains in search of fresh pasture and return south around October. This great migration is one of the most impressive natural events in the world.