The Copernicus Sentinel-3 satellite takes us over eastern US. Spanning a huge area, including the states of Ohio, Maryland, West Virginia and Delaware, a number of major cities can be seen in this true-colour image. The megacity of New York is visible in the top right. A megacity is defined by the United Nations as a city with a population of over ten million. According to the latest estimates there will be 43 megacities across the globe by 2030.