The place
Nyerere, in short.
Nyerere was created in 2019 out of the northern, photographic part of the old Selous Game Reserve. The name changed; the country did not. It is a floodplain park on an enormous scale, defined by the Rufiji River and the chain of lakes it feeds.
The water is the point. Almost nowhere else in Tanzania can you spend a morning on a boat among hippo and elephant and an afternoon walking the same bank. That combination — drive, boat, walk — is why people come here rather than to a northern park.
It also holds one of the most important remaining populations of African wild dog. Sightings are never guaranteed anywhere, but if you want a realistic chance, this is where to spend your nights.