The Indus Valley Civilization, one of the world's first urban societies, flourished along the Indus River in present-day India and Pakistan, showcasing advanced city planning, a sophisticated drainage system, and early forms of writing and trade. Key features included well-structured cities like Harappa and Mohenjo-Daro, skilled craftsmanship, agricultural practices, and an economy based on trade with neighboring regions. The civilization experienced a decline around 1900 B.C., with theories attributing it to disease, natural disasters, or invasions.