Tokyo, seen here at night from the International Space Station, is the most populous metropolitan area in the world with upwards of 37.8 million people.
This photograph is courtesy of NASA's “Cities at Night” project. Through this effort, NASA has invited the public to sift through its collection of more than 1.8 million photographs captured from the ISS since 2003. With crowdsourcing, we will be able to identify and catalogue the cities on Earth that have been captured so far!
Source: Alejandro Sánchez de Miguel, José Gómez Castaño, Jaime Zamorano, Christopher CM Kyba, Sergio Pascual,M Ángeles, L Cayuela, Guillermo Martín Martinez and Peter Challupner, Atlas of astronaut photos, of Earth at night, News and Reviews in Astronomy & Geophysics, Vol. 55 no4. August 2014 (in press).