The Indus Valley Civilization began during the Bronze Age between 2500 BC and 1500 BC in the Indus River valley region spanning modern day Pakistan and northwest India. Two major cities, Mohenjo-Daro and Harappa, had highly developed urban planning with large residential areas, wells, bathrooms, and an effective drainage system. The people practiced burial rituals, usually in a north-south orientation, and buried individuals with jewelry. The civilization declined around 1800 BCE for reasons that are still unclear but may have included flooding of the Saraswati River or other catastrophic events disrupting the agricultural economy and civic order.