Clue
This Landsat 7 color image from 1999 shows a portion of a large city (lower right) that lies in a river valley in an arid region of Africa. On the outskirts of the city there are several large man-made structures that are thousands of years old. The box on the image indicates this area, enlarged in a high resolution Landsat 7 image (lower left). Name the city.
Landsat Images courtesy of USGS/EROS Data Center