the red sand dunes in Sossusvlei are more than 300m high, if you are lucky, the "vlei" is filled with water which gives the place a surreal, fata morgana like impression;
climb on one of the sanddunes to see the desert extend in all directions

Koakaveld is one of the last great wildernesses in Africa; Himbas live here as they have for centuries;
if you can not go on a longer trip into the Koakofeld (which requires two four wheel drive vehicles + all supplies) you can spent the night in Sesfontain, a restored castle that has been converted into a hotel and make day trips to see a Himba village and to look for desert elephants. You can also just enjoy the nice pool.

The MET (Ministry of Environment & Tourism) has camps in many of the national parcs, we specially recommend Namutoni in Etosha and the Bernabe de la Bat Rest Camp, Waterberg; you can book the camps in the MET offices in Windhoek, Swakopmund or Lüderitz

If you can spare a bit of cash, stay a night at this guest farm (safari lodge), As home of the AFRICAT foundation, they manage a rehabilitation center to re-introduce cheetahs and leopards into the wild. It will cenrtainly higher your adrenalin level, when you are face to face with a cheetah