Megacities are the largest urban areas in the world.
A megacity is defined as having a population greater than 10 million people. Previous definitions used greater than 8 million.
There are over 34 megacities in the world. The largest megacity is Tokyo-Yokohama with approximately 38 million people.
In addition to population, megacities often cover a large area (urban sprawl). Metropolitan areas that are close together may merge into a metroplex.
