Clusters of yellow lights on the Indo-Gangetic Plain reveal numerous cities large and small in northern India and northern Pakistan. Of the hundreds of clusters, the largest are the capital cities of Islamabad (bottom), Pakistan, and New Delhi (top), India. The lines of major highways connecting the cities also stand out. More subtle, but still visible at night, are the general outlines of the towering and partly cloud-covered Himalayas to the north (image left). A striking feature is the line of lights, with a distinctly orange hue, snaking across the centre of the image. It appears to be more continuous and brighter than most highways in the view. This is the fenced and floodlit border zone between India and Pakistan, designed to discourage smuggling and arms trafficking

Photograph: ISS/NASA