Cairo has become so crowded, congested and polluted that the Egyptian government has undertaken a construction project that might have given the Pharaohs pause: building two megacities outside Cairo from scratch. By 2020, planners expect the new satellite cities to house at least a quarter of Cairo’s 20 million residents and many of the government agencies that now have headquarters in the city.
As the author notes, only a country with limitless supply of open albeit desert land and an authoritarian government can come up with such a solution. Something similar was planned and executed on the mainland to ease Mumbai's (India) problem. Last I heard, the nodes of Navi Mumbai (New Bombay) had a population of nearly 3 million and rising.