Riyadh is the capital and largest city of Saudi Arabia, populated by about 7 million people. The city has grown explosively from an isolated town into a metropolis since the 1940s. Although located in an area with only ~100 mm of yearly rainfall, the city has sufficient drinking water reservoirs. The reservoirs are replenished from rain water, ground water, and desalinated coastal water. The image shows the Riyadh urban area in the center, surrounded by the Arabian desert to the east and Tuwaiq mountains to the south.