The endless plains and grassland of Africa.
As Tanzania's oldest and largest National Park and one of the world's best know wildlife sanctuaries, the 14763 km² Serengeti National Park constitutes one of the jewels in Tanzania's wildlife crown.
The name Serengeti comes from the Maasai word Siringeti, referring to an endless plain. As you stand on the southern plains you experience this vastness and can be the witness of one of the greatest consecrations of plain animals left on earth.
The plains were formed 3-4 million years ago when ash blown from volcanoes in the Ngorongoro highlands covered the rolling landscape. These thick layers of ash preserved faces of early humans, and established the rich soil which supports the southern grass plains. From this early beginning men and wildlife have shared this magical place.
The park stretches from the highland plateau of the Ngorongoro in the south to the mountainous slopes of Isuria in the north. It reaches as far as to Lake Victoria in the west in the form of a wide corridor. The altitude varies between 920m and 1850m above sea level. The Soronera area being located at 1530m.
The originality of this park lies in its great variety of environments, wide grass plains to the south, acacia savannah in the central region, more densely wooded hills to the north and in the western corridor a vast woodland area with mountains overlooking the plains.
The diversity of the scenery – plains with rivers and lakes here, hills and granite outcrops called kopjes (pronounced kop-yees; from the Afrikaans for little head) there – transmits the feeling of an infinite variety and incomparable wildness.
According to the seasons the Serengeti changes from a rich fertile land to a desolated wildness, causing the spectacular migration of millions of herbivores: the cause why people come to Serengeti. And the figures are flabbergasting of the five million animals to be found during the migration (double the resident populations). There are wildebeests, who are numbered 1.7 million at the last count, gazelles, both grants and thomsons who are estimated at around half a million, and some 300.000 zebras. The park contains substantial populations of plains game including buffalo, giraffe and warthog, as well as a wide range of antelopes, including dik diks, bushbucks, water bucks and mountain reedbucks, elands, impalas and rarer oryx and topis. Some 1500 elephants, too, are present though they are largely migratory and can easily be missed.
But all this is to forget perhaps the most memorable of all Serengeti animals, its predators. The Serengeti is probably the best place in Tanzania to see predators in action apart from Ngorongoro. There are nearly eight thousands much-maligned sported hyenas, which live in clans of up to eighty.
Also very visible are the park's three thousand or so lions, other predators including cheetahs which have been the subject of ongoing research since 1975, leopards and bat-eared foxes, scavengers, apart from hyenas (who also hunt), including both golden and side striped jackals and vultures. 520 birds species (including Eurasian winter migrants) and 34 raptors (birds of pray).
Short rains fall between November and December, while the long rains are from February or March until the end of May.
The Wildlife Migration passes through the Serengeti between December and July. The Serengeti owns its hallowed place in our immigration to the annual 800km migration of over 2.5 million animals, the largest mammalian migration on earth.
The migrations ease less movement is prompted by a seasonal search for fresh water and pastures dictated by the rains. It moves in a roughly clockwise direction, concentrating in the National Park from April to June towards the end of the long rains, before leaving behind the withering plains of the Serengeti by journeying northward towards the fresh moisture and grass of Kenya's Maasai Mara game reserve, which the migration reaches in August. By September and October the bulk of the migration is concentrated in Maasai mara. By late October and early November the Mara's grasslands are approaching exhaustion, so the migration turns back towards the northern and eastern Serengeti, following the fresh grass brought by the short rains. During this period the migration is widely spread out and a large part of it cycles through Loliondo and into Ngorongoro beyond the Serengeti's eastern border. From December to March the migration settles in the Serengeti plains and western Ngorongoro, where it remains until the onset of the long rains. 
The wildebeests take advantage of this temporary pause to give birth (especially from late January to mid March) accounting for half a million calves annually. The timing of the mass birthing provides security in numbers, predators will eat their fill but within a few months the surviving calves are much stronger and able to outrun their pursuers; nonetheless the hazards of the migration are such that only one in three calves makes it back the following year. By April the migration is once more concentrated inside the Serengeti and the whole cycle starts again.
The exact time and location of the migration varies annually, depending on the rains and other factors, so coinciding with it cannot be guaranteed.