The Indus River Valley Civilization developed along the Indus River in modern-day Pakistan and northwest India. The Indus flows southwest into the Arabian Sea and provided water, fertile soil, and transportation for the early Indian civilization. Some key cities of the Harappan civilization included Harappa and Mohenjo-Daro, which were carefully planned with wide streets in a grid pattern and advanced sewer systems. While their written language remains undeciphered, the Harappans grew crops, traded, and showed little evidence of war in their art. The citadel in cities could store enough grain for tens of thousands, indicating they planned for potential crop failures from monsoons.