Buildings, streets, and people pack tightly together. An urban area is a densely developed territory characterized by continuous built-up land and high population density. It includes the central city and its immediate suburbs.

Urban areas concentrate economic activity, innovation, and cultural institutions. They also generate distinctive environmental problems—air pollution, heat islands, and waste. Definitions vary by country, but the essential contrast is with rural landscapes of lower density and more open land.

The world’s urban population has surpassed the rural population. Managing urban growth, housing, and infrastructure is a central challenge of the twenty-first century. Urban areas continue to expand outward and upward as they absorb migration and natural increase.

• Densely built-up and populated territory
• Includes city centers and contiguous suburbs
• Focus of economic and cultural activity
• Growing share of global population