We walked a few miles to get here from the wonderful Olduvai Camp. It is a great little museum that does a good job of explaining the history and significance of this place. I appreciated the talk given by a local paleontologist who spoke very...slowly, which allowed my brain to comprehend some of the vast time scale involved ;)
To correct the previous post, you CAN go down into the gorge but you have to pay extra and it is very hot and tiring. We stayed at the viewing deck where you can get a good sense of the geology from above.