Ngorongoro Crater, Tanzania

I ran across an interesting book sitting in a hotel lobby recently that looks like an excellent 'bucket list' of travel locations -- 100 Wonders of the World 

I'm sure I'll refer to a few more locations in that book but the Ngorongoro Crater in Tanzania was instantly compelling.

http://en.wikipedia.org/wiki/Ngorongoro_Conservation_Area

Click on the image below, it's huuuuge.

It's also close to the Serengeti, another place that appears amazing.
http://en.wikipedia.org/wiki/Serengeti