Source of the photo
http://www.learner.org/courses/envsci/unit/text.php?unit=5&secNum=6
Author of the description
Gruiz, Katalin
The map shows the prognosis for 2015.
The largest cities will reach or exceed 30 millions for 2015. These are: Mexico City, Sao Paolo in Brazil, Mumbai and Delhi in India and Tokio.
Source of description
Worldwatch Institute, State of the World 2007: Our Urban Future