Udzungwa Mountains National Park

Udzungwa Maountanis National Park is a paradise fir hikers and one of Tanzania's most beautiful wilderness areas. Its most striking feature,apart from its mountanious terrain, is its pristine and biologically diverse forest which hosts a variety of animal and plant species not found anywhere else in the world. Among its residents are six species of primates, including the rare Iringa red colobus and the Sange crested mangabey monkeys, as well as populations of elephant, buffalo, leopard, and a rich variety of birdlife. The rare Udzungwa partridge is endemic to the area and has been sighted near the park's boundaries.The high degree of endemism and biodiversity that characterrises Udzungwa is due mainly to the area's constant climate over millions of years, which has given species a chance to evolve. Anotherfactor is Udzungwa (at approximately 200m) to Luhombero peak (2579m), there is essentially continuous forest. The area is one of the few places in Africa with continuous rainforest over such a great span.
There are no roads in Udzungwa; instead, there are about four major and several lesser hiking paths winding through various sectins of the park. Popular hikes include a short but steep half-day hike to Sange waterfalls, and a two day climb to the to of  Luhobero, Udzungwa's highest peak.
Udzungwa, whickh has an area of 1900 sq km, was gazetted in 1992 and is Tanzania's newest national park. (lonely planet)

Ruaha National Park

Ruaha National Park is a vast wilderness area which hosts one of the largest elephant populations in Africa. In addition to the elephants, which are estimated to a number at least 12,000, the park has large herds of buffalo,as greater as well as greater and lesser kudo, Grant's gazelle, wild dog, ostrich, cheetah, sable antelope, and more than 400 different bird species. The Great Ruaha River flows through the eastern side of the park and is home to hippo, crocodile and many water birds.
      With an area of almost 13,000 sq km, Ruaha National Park is Tanzania's second largest, and is part of an extended ecosystem that also encompasses the adjoining Rungwa and Kisigo game reserves. Much of the park is undulating plateau everanging about 900m in height with occasional rocky outcrops, and mountains in the south and west reaching to about 1600m and 1900m, respectively.
       Large areas of Ruaha are unexplored and undeveloped; one of the park management's goals is to preserve as much of the territory as possible in a pristine and undisturbed state. Due to Ruaha's vastness and character, you should set aside as much time as you can spare to visit; it's not a place to be discovered on a quick in and out trip. (lonely planet)

Selous Game Reserve

With an area of approx. 50,000 sq km, the Selous is Africa's largest game reserve covering 5% of Tanzania's total land area. The reserve provides shelter for more than half of the country's elephant, as well as significant populations of buffalo, wild dog, crocodile and hippo, a rich variety of birdlife, and some of Tanzania's last remaining black rhino.
       Parts of the reserve were set aside as early as 1905, although it was not until 1922 that the area wa expanded and given its present name (after Frederick Courteney Selous, The British explorer who was killed in the reserve during WWI). The area continued to be extended over the next several decades until assuming its present boundaries in 1975.
       One of the main features of the Selous is the huge Rufuji River, which has one of the largest water catchment areas in East Africa. In the northern end of the reserve, where the Great Ruaha River flows into the Rufiji, is Stiegler's Gorge. The gorge, which averages 00m deeep, is named after a German explorer who was killed here by an elephant in 1907. Most of the safari camps and lodges are in this area.

Mikumi National Park

Mikumi is Tanzania's thiird largest national park and the most accessible from Dar es Salaam. It's an idela place for those who do not have a lot of time, but want to see a large variety of wildlife. Withn its 3230 sq km set between the Uluguru mountains to the north and the Lumango mountains to the south-east, Mikumi hosts populations of buffalo, giraffe, elephant, lion, zebra, leopard, crockodile and many others. It is likely that you'll see at least some of these within just a short time of entering the park. Although Mikumi receives comparatively few visitors, those who do come rearly leave disappointed. In the section of the park to the west of the main road, there is a hippo pool which provides an excellent opportunity to watch the animals at a close range. This is also a good place for observing varied water birds.
        Mikumi is a significant educational and research centre. Among the vrious projects being carried out is an ongoing field study of yellow baboons, which are numerous here. It's on of just a handful of such longterm primate studies on the continent.
        To the west of Mikumi, around Mbuyuni, is an enomorous and striking collection of  baobab trees stretching along the side of the main road. (lonely planet)