Which canyon, located in Tanzania, is famous for its fossil beds?
The site you are thinking of is not quite big enough to be labeled a canyon—it's more of a gorge.
The Olduvai Gorge is a 30-mile long, 295-foot-deep ravine located in Tanzania's Serengeti National Park in east Africa. It is one of the most successful archaeological sites in the world.
Some of the oldest human fossil remains have been unearthed there. The most famous discovery occurred in 1959 when British archeologist Mary Leakey (along with her husband Louis) discovered remains of a man they named "Nutcracker Man" (because of the extra-large molars) that are believed to be 1.75 million years old.
For more information about prehistoric humans, check out our Life Sciences section.