Journeys to four mega-cities to investigate a major challenge of the 21st Century, how to shelter and sustain the world's exploding urban population without destroying the delicate balance of our environment. Mexico City: Communities struggle with toxic smog and a dwindling supply of drinking water, while nearby farmers must cope with the city's untreated waste. Istanbul: At the crossroads of Asia and Europe, this ancient city's infrastructure is strained by more than half a million new residents each year. Shanghai: In the midst of an economic boom, rapid urbanization has increased air and water pollution and caused a dramatic loss of farmland to industrial sprawl. New York City: Though most of the city can boast clean air and water, for some, environmental inequality has resulted in serious health problems.

CIRC # 402\\Originally broadcast as an episode of Journey to planet Earth on PBS in 2009. Special features: Abridged version (30 min.); Educators' guides (DVD-ROM). Public performance video.

Mexico City -- Istanbul -- Shanghai -- New York City.