The Indus Valley Civilization was one of the world's earliest urban civilizations located in northwestern India and eastern Pakistan. It flourished between 3300 BCE and 1300 BCE, covering over 1 million square kilometers. Major cities included Harappa and Mohenjo-Daro, which had sophisticated urban planning with standardized bricks, sewage systems, and multi-story buildings. The Indus Valley Civilization developed new agricultural, metallurgical, and craft techniques and engaged in extensive regional trade. Around 1800 BCE, the civilization began to decline due to changing climate or flooding of the Ghaggar Hakra river system, and most cities were abandoned by 1300 BCE.