For people traveling to Tanzania and the Serengeti, the Ngorongoro Crater is a must. However, I would recommend starting your African Safari with the Crater. We did the Crater at the end of our safari, and it was a bit of a let down after the tranquil vastness of the Serengeti.
All accommodations are outside the Crater, so we took a very early drive to get there and then to get down into the Crater. There was no visibility due to an immense fog, which made me happy that I was not driving. You can only enter the Crater through a tour company.
The Ngorongoro Crater is rich with vegetation and water, which is why many creatures have made this their permanent home. We mostly wanted to see lion cubs as we missed that in the Serengeti, and that was one of the first things we saw (pictured above). There were three adorable cubs playing with each other. The hippo pool is wonderful as well. You could spend hours there watching them play (pictured below). I think the only thing I really disliked about the adventure in the Ngorongoro Crater was the fact that it is pretty crowded with tourists. After a week in the Serengeti, where it felt like it was just you and the animals, the Crater was heavily populated with humans. We had to wait to get a spot to view the hippos. I still find the place very interesting and feel that it is a must see.
If you are looking for a nice place to stay while you visit the Ngorongoro Crater, I highly recommend Gibbs Farm. Gibbs Farm (pictured on the right) is located on a coffee 
plantation, which you can venture through. It is a simple yet luxurious retreat. Wi-fi is a bit unreliable, but with all the beautiful scenery, delicious foods, and fun activities, who needs Wi-fi? Each room is like your own secluded bungalow, where I enjoyed my first outdoor bathing experience. After a week in the wilderness, it was a welcome relaxing retreat.
I would say that a couple days of viewing the Ngorongoro Crater is all you need, but it is worth it!
The Great Morrison Migration 