The desert 20km south of Bawati is covered with the dark conical masses of former volcanic hills that used to be buried and have since been eroded by time. The visual effect is of solitary mountains seemingly piercing the sand. Erosion has left bits of basalt and iron pyrite strewn about, and this is how the desert got its name. Along the roadside, you can climb Black Mountain (or Gebel Gala Siwa), a former observation post for caravans with panoramic views of the desert from the summit.