A megalopolis is a large, densely populated urban area that typically consists of multiple cities and their suburbs that have grown together due to population expansion and economic integration. These regions often feature extensive infrastructure and significant cultural, political, and economic influence. Examples include the Northeast U.S. corridor stretching from Boston to Washington, D.C., and the Tokyo-Yokohama area in Japan. Megalopolises can face challenges such as congestion, pollution, and resource management due to their size and population density.