The document summarizes the Indus Valley Civilization, one of the earliest civilizations in South Asia. It emerged around 2500 BCE in the Indus River Valley in modern-day Pakistan and lasted over 1000 years. Archaeologists have uncovered two major cities, Harappa and Mohenjo-Daro, which had populations of around 80,000 people and advanced infrastructure like planned streets, drainage systems, and public baths. However, the civilization mysteriously declined around 1900 BCE for unknown reasons that could include ecological disasters or invading groups.