The Indus Valley Civilization arose around 2500 BC along the Indus River valley, lasting over 1000 years. Archaeologists have uncovered large cities like Harappa and Mohenjo-Daro that had planned streets and fortresses, suggesting a well-organized government. Farmers grew crops and traded with other regions. While the writing system remains undeciphered, statues depict religious worship of female and animal gods. The decline of this civilization around 1500 BC may have been due to climate change and flooding. Later, Aryan groups migrated in and their religious traditions were recorded in the Vedas, establishing a social hierarchy.