The sand dunes of the Sahara can grow taller than a ten-storey building, shaped by the wind into smooth curves and sharp ridges. But not all of the Sahara is sand — in fact, most of it is rocky ground called 'reg', flat and stony and stretching as far as the eye can see. Sand dunes are called 'erg' and they cover about a quarter of the desert.
Animals that live in the Sahara have amazing adaptations. Fennec foxes have enormous ears that act like radiators to let heat escape from their bodies. Addax antelopes barely need to drink water at all — they get almost all the moisture they need from the plants they eat. Beetles collect water from morning fog by doing a special 'fog-stand', tilting their bodies so tiny water drops roll down into their mouths.
At night, the Sahara becomes breathtakingly beautiful. Because there are very few towns or electric lights, the night sky over the desert is one of the clearest in the world. You can see the Milky Way stretching across the sky like a river of stars, and temperatures drop sharply — it can go from very hot in the day to near-freezing at night.